diff --git a/build.rs b/build.rs
index dc57811..d4b8708 100644
--- a/build.rs
+++ b/build.rs
@@ -3,6 +3,17 @@ use std::{
     path::Path,
 };
 
+const RENAMES: &[(&str, &str)] = &[
+    ("CUsizeResult", "size_t"),
+    ("CIsizeResult", "ssize_t"),
+    ("CEofResult", "int"),
+    ("CIntCountResult", "int"),
+    ("CIntZeroResult", "int"),
+    ("CFdResult", "int"),
+    ("COffsetResult", "off_t"),
+    ("CPidResult", "pid_t"),
+];
+
 fn include_dir(d: &DirEntry) -> bool {
     d.metadata().map(|m| m.is_dir()).unwrap_or(false)
         && d.path()
@@ -26,7 +37,12 @@ fn generate_header<P: AsRef<Path>>(config_path: P) {
         .with_extension("h");
     let mod_path = config_path.with_file_name("mod.rs");
 
-    let config = cbindgen::Config::from_file(config_path).unwrap();
+    let mut config = cbindgen::Config::from_file(config_path).unwrap();
+
+    config
+        .export
+        .rename
+        .extend(RENAMES.into_iter().map(|&(x, y)| (x.into(), y.into())));
 
     cbindgen::Builder::new()
         .with_config(config)
diff --git a/src/allocator.rs b/src/allocator.rs
index e49e450..8b3a20d 100644
--- a/src/allocator.rs
+++ b/src/allocator.rs
@@ -1,4 +1,81 @@
+use core::{
+    alloc::{GlobalAlloc, Layout},
+    intrinsics,
+    ptr::NonNull,
+};
+
 use libyalloc::global::GlobalAllocator;
+use yggdrasil_rt::memcpy;
+
+use crate::{error::EResult, header::errno::ENOMEM, util::NonNullExt};
 
 #[global_allocator]
 pub static GLOBAL_ALLOCATOR: GlobalAllocator = GlobalAllocator;
+
+const ALIGN: usize = 16;
+const OFFSET: usize = ALIGN;
+
+unsafe fn get_allocation(ptr: NonNull<u8>) -> (NonNull<u8>, Layout) {
+    assert!(usize::from(ptr.addr()) > 0x10);
+    let real_ptr = ptr.sub_ext(OFFSET);
+    let size = *real_ptr.cast::<u64>().as_ref();
+    let layout = Layout::from_size_align(size.try_into().unwrap(), ALIGN).unwrap();
+    (real_ptr, layout)
+}
+
+// TODO checked_add here
+pub fn c_allocate(size: usize) -> EResult<NonNull<u8>> {
+    let size = (size + ALIGN - 1) & !(ALIGN - 1);
+    let layout = Layout::from_size_align(size + OFFSET, ALIGN).unwrap();
+
+    let ptr = match NonNull::new(unsafe { GlobalAllocator.alloc(layout) }) {
+        Some(ptr) => ptr,
+        None => return EResult::Err(ENOMEM),
+    };
+
+    // Store allocation size
+    unsafe {
+        *ptr.cast::<u64>().as_mut() = layout.size().try_into().unwrap();
+    }
+
+    unsafe { EResult::Ok(ptr.add_ext(OFFSET)) }
+}
+
+pub fn c_allocate_zeroed(nmemb: usize, size: usize) -> EResult<NonNull<u8>> {
+    match nmemb.checked_mul(size) {
+        Some(size) => {
+            let ptr = c_allocate(size)?;
+            unsafe {
+                intrinsics::write_bytes(ptr.as_ptr(), 0, size);
+            }
+            EResult::Ok(ptr)
+        }
+        None => EResult::Err(ENOMEM),
+    }
+}
+
+pub unsafe fn c_reallocate(old_ptr: Option<NonNull<u8>>, size: usize) -> EResult<NonNull<u8>> {
+    match old_ptr {
+        Some(old_ptr) => {
+            // TODO libyalloc realloc
+            let (real_old_ptr, old_layout) = get_allocation(old_ptr);
+            let new_ptr = c_allocate(size)?;
+
+            memcpy(
+                new_ptr.cast().as_ptr(),
+                old_ptr.cast().as_ptr(),
+                old_layout.size() - OFFSET,
+            );
+
+            GlobalAllocator.dealloc(real_old_ptr.as_ptr(), old_layout);
+
+            EResult::Ok(new_ptr)
+        }
+        None => c_allocate(size),
+    }
+}
+
+pub unsafe fn c_free(ptr: NonNull<u8>) {
+    let (real_ptr, layout) = get_allocation(ptr);
+    GlobalAllocator.dealloc(real_ptr.as_ptr(), layout);
+}
diff --git a/src/error.rs b/src/error.rs
index 9cebef6..2cd5bab 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -2,138 +2,378 @@ use core::{
     convert::Infallible,
     ffi::c_int,
     ops::{ControlFlow, FromResidual, Try},
+    ptr::{null_mut, NonNull},
 };
 
-use crate::header::{errno::Errno, stdio::EOF};
+use yggdrasil_rt::io::RawFd;
 
-pub trait CZeroResult {
-    fn into_zero_status(self) -> c_int;
-    fn into_eof_status(self) -> c_int;
+use crate::header::{
+    errno::{Errno, EBADF},
+    stdio::EOF,
+    sys_types::{off_t, pid_t},
+};
+
+/// On success: count
+/// On failure: 0
+///
+/// Examples:
+///
+/// fwrite()/fread() functions
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CUsizeResult(pub usize);
+
+/// On success: count
+/// On failure: -1
+///
+/// Examples:
+///
+/// read()
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CIsizeResult(pub isize);
+
+/// On success: count
+/// On failure: -1
+///
+/// Examples:
+///
+/// printf() family of functions
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CIntCountResult(pub c_int);
+
+/// On success: 0
+/// On failure: -1
+///
+/// Examples:
+///
+/// ftrylockfile()
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CIntZeroResult(c_int);
+
+/// On success: file descriptor
+/// On failure: -1
+///
+/// Examples:
+///
+/// open()/fileno()
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CFdResult(c_int);
+
+/// On success: pid_t
+/// On failure: -1
+///
+/// Examples:
+///
+/// fork()
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CPidResult(pid_t);
+
+/// On success: some non-EOF value
+/// On failure: EOF
+///
+/// Examples:
+///
+/// fputc()/fgetc()
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CEofResult(pub c_int);
+
+/// On success: a valid off_t
+/// On failure: -1
+///
+/// Examples:
+///
+/// ftello()
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct COffsetResult(pub off_t);
+
+/// On success: NonNull ptr
+/// On failure: NULL
+///
+/// Examples:
+///
+/// malloc()/fgets()
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+#[repr(transparent)]
+pub struct CPtrResult<T>(*mut T);
+
+impl FromResidual<EResult<Infallible>> for CUsizeResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self(0)
+    }
 }
 
-pub trait CSizeResult {
-    fn into_size_status(self) -> usize;
+impl CIsizeResult {
+    pub const ERR: Self = Self(-1);
+
+    pub fn success(value: usize) -> Self {
+        Self(value.try_into().unwrap())
+    }
 }
 
-pub trait TryFromExt<T>: Sized {
-    fn e_try_from(value: T) -> EResult<Self>;
+impl FromResidual<EResult<Infallible>> for CIsizeResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self(-1)
+    }
 }
 
-pub trait OptionExt<T> {
-    fn e_ok_or(self, err: yggdrasil_rt::Error) -> EResult<T>;
+impl FromResidual<EResult<Infallible>> for CIntCountResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self(-1)
+    }
 }
 
-// TODO thread_local
-#[no_mangle]
-pub static mut errno: Errno = Errno(0);
-
-pub enum EResult<T> {
-    Ok(T),
-    Err(yggdrasil_rt::Error),
-    Errno(Errno),
+impl CIntZeroResult {
+    pub const ERR: Self = Self(-1);
+    pub const OK: Self = Self(0);
 }
 
-impl<T> From<Result<T, yggdrasil_rt::Error>> for EResult<T> {
-    fn from(value: Result<T, yggdrasil_rt::Error>) -> Self {
-        match value {
-            Ok(value) => Self::Ok(value),
-            Err(error) => Self::Err(error),
+impl FromResidual<EResult<Infallible>> for CIntZeroResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self::ERR
+    }
+}
+
+impl CFdResult {
+    pub const ERR: Self = Self(-1);
+
+    pub fn success(fd: RawFd) -> Self {
+        Self(fd.0.try_into().unwrap())
+    }
+}
+
+impl FromResidual<EResult<Infallible>> for CFdResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self::ERR
+    }
+}
+
+impl CEofResult {
+    pub const ERR: Self = Self(EOF);
+
+    pub fn ok(&self) -> Option<c_int> {
+        match self.0 {
+            EOF => None,
+            v => Some(v),
         }
     }
 }
 
+impl FromResidual<EResult<Infallible>> for CEofResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self::ERR
+    }
+}
+
+impl COffsetResult {
+    pub const ERR: Self = Self(-1);
+
+    pub fn ok(self) -> Option<i64> {
+        if self.0 >= 0 {
+            Some(self.0)
+        } else {
+            None
+        }
+    }
+
+    pub fn success(value: u64) -> Self {
+        Self(value.try_into().unwrap())
+    }
+}
+
+impl FromResidual<EResult<Infallible>> for COffsetResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self::ERR
+    }
+}
+
+impl CPidResult {
+    pub const ERR: Self = Self(-1);
+
+    pub fn success(pid: u32) -> Self {
+        Self(pid.try_into().unwrap())
+    }
+}
+
+impl FromResidual<EResult<Infallible>> for CPidResult {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self::ERR
+    }
+}
+
+impl<T> CPtrResult<T> {
+    pub const ERR: Self = Self(null_mut());
+
+    pub const fn success(value: NonNull<T>) -> Self {
+        Self(value.as_ptr())
+    }
+}
+
+impl<T> FromResidual<EResult<Infallible>> for CPtrResult<T> {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        unsafe {
+            errno = err;
+        }
+        Self::ERR
+    }
+}
+
+/////////////////
+
+#[must_use = "ErrnoResult<T> must be converted into its output type with proper errno set"]
+pub enum EResult<T> {
+    Ok(T),
+    Err(Errno),
+}
+
 impl<T> EResult<T> {
-    pub fn into_set_errno(self) -> EResult<T> {
+    pub fn is_ok(&self) -> bool {
+        matches!(self, Self::Ok(_))
+    }
+
+    pub fn is_err(&self) -> bool {
+        matches!(self, Self::Err(_))
+    }
+
+    pub fn ok(self) -> Option<T> {
         match self {
-            Self::Ok(value) => Self::Ok(value),
-            Self::Errno(e) => Self::Errno(e),
+            Self::Ok(value) => Some(value),
+            Self::Err(_) => None,
+        }
+    }
+
+    pub fn unwrap(self) -> T {
+        todo!()
+    }
+
+    pub fn unwrap_err(self) -> Errno {
+        match self {
+            Self::Ok(_) => panic!("Expected an error"),
+            Self::Err(err) => err,
+        }
+    }
+
+    pub fn into_result<E, F: Fn(Errno) -> E>(self, map_err: F, set_errno: bool) -> Result<T, E> {
+        match self {
+            Self::Ok(value) => Ok(value),
             Self::Err(err) => {
-                let e = Errno::from(err);
-                unsafe {
-                    errno = e;
+                if set_errno {
+                    unsafe {
+                        errno = err;
+                    }
                 }
-                Self::Errno(e)
+                Err(map_err(err))
             }
         }
     }
 }
 
-impl CZeroResult for Result<(), Errno> {
-    fn into_zero_status(self) -> c_int {
-        match self {
-            Self::Ok(_) => 0,
-            Self::Err(_) => -1,
-        }
-    }
-
-    fn into_eof_status(self) -> c_int {
-        match self {
-            Self::Ok(_) => 0,
-            Self::Err(_) => EOF,
-        }
-    }
-}
-
-impl CSizeResult for Result<usize, Errno> {
-    fn into_size_status(self) -> usize {
-        match self {
-            Self::Ok(value) => value,
-            Self::Err(_) => 0,
-        }
-    }
-}
-
-impl<T> FromResidual<Errno> for EResult<T> {
-    fn from_residual(residual: Errno) -> Self {
-        Self::Errno(residual)
-    }
-}
-
-impl<T> FromResidual<yggdrasil_rt::Error> for EResult<T> {
-    fn from_residual(residual: yggdrasil_rt::Error) -> Self {
-        Self::Err(residual)
-    }
-}
-
-impl<T> FromResidual<Result<Infallible, Errno>> for EResult<T> {
-    fn from_residual(_residual: Result<Infallible, Errno>) -> Self {
-        todo!()
-    }
-}
-
 impl<T> Try for EResult<T> {
     type Output = T;
-    type Residual = Result<Infallible, Errno>;
+    type Residual = EResult<Infallible>;
 
     fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
-        match self.into_set_errno() {
+        match self {
             Self::Ok(value) => ControlFlow::Continue(value),
-            Self::Errno(e) => ControlFlow::Break(Err(e)),
-            Self::Err(_error) => unreachable!(),
+            Self::Err(err) => ControlFlow::Break(EResult::Err(err)),
         }
     }
 
-    fn from_output(_output: Self::Output) -> Self {
-        todo!()
+    fn from_output(output: Self::Output) -> Self {
+        Self::Ok(output)
     }
 }
 
+impl<T> FromResidual<EResult<Infallible>> for EResult<T> {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        Self::Err(err)
+    }
+}
+
+impl<T> FromResidual<Result<Infallible, yggdrasil_rt::Error>> for EResult<T> {
+    fn from_residual(residual: Result<Infallible, yggdrasil_rt::Error>) -> Self {
+        let err = residual.unwrap_err();
+        Self::Err(err.into())
+    }
+}
+
+impl<T, E: From<Errno>> FromResidual<EResult<Infallible>> for Result<T, E> {
+    fn from_residual(residual: EResult<Infallible>) -> Self {
+        let err = residual.unwrap_err();
+        Err(err.into())
+    }
+}
+
+///////////////////////////////////////////////
+
+pub trait OptionExt<T> {
+    fn e_ok_or(self, err: Errno) -> EResult<T>;
+}
+
 impl<T> OptionExt<T> for Option<T> {
-    fn e_ok_or(self, err: yggdrasil_rt::Error) -> EResult<T> {
+    fn e_ok_or(self, err: Errno) -> EResult<T> {
         match self {
-            Some(value) => EResult::Ok(value),
+            Some(val) => EResult::Ok(val),
             None => EResult::Err(err),
         }
     }
 }
 
-pub fn set_errno_result<T>(e: Errno) -> Result<T, Errno> {
-    set_errno(e);
-    Err(e)
+///////////////////////////////////////////////
+
+pub trait TryFromExt<T>: Sized {
+    fn e_try_from(value: T) -> EResult<Self>;
 }
 
-pub fn set_errno(e: Errno) {
-    unsafe {
-        errno = e;
+impl TryFromExt<c_int> for RawFd {
+    fn e_try_from(value: c_int) -> EResult<Self> {
+        match value {
+            0.. => EResult::Ok(Self(value.try_into().unwrap())),
+            _ => EResult::Err(EBADF),
+        }
     }
 }
+
+// TODO thread_local
+#[no_mangle]
+pub static mut errno: Errno = Errno(0);
diff --git a/src/file.rs b/src/file.rs
index 907d238..27f3e94 100644
--- a/src/file.rs
+++ b/src/file.rs
@@ -10,8 +10,7 @@ use yggdrasil_rt::{
 };
 
 use crate::{
-    error::{self, EResult},
-    header::errno::{Errno, EBADF},
+    error::{EResult, TryFromExt},
     io::{AsRawFd, AsRawFdOpt, FromRawFd, IntoRawFd, Read, Seek, Write},
 };
 
@@ -36,42 +35,41 @@ impl RawFile {
         pathname: P,
         opts: OpenOptions,
         mode: FileMode,
-    ) -> Result<Self, Errno> {
-        let fd =
-            EResult::from(unsafe { syscall::open(at, pathname.as_ref().as_str(), opts, mode) })?;
-        Ok(Self { fd })
+    ) -> EResult<Self> {
+        let fd = unsafe { syscall::open(at, pathname.as_ref().as_str(), opts, mode) }?;
+        EResult::Ok(Self { fd })
     }
 
-    pub unsafe fn close(self: &mut Self) -> Result<(), Errno> {
-        EResult::from(unsafe { syscall::close(self.fd) })?;
+    pub unsafe fn close(self: &mut Self) -> EResult<()> {
+        unsafe { syscall::close(self.fd) }?;
         self.fd = RawFd::NONE;
-        Ok(())
+        EResult::Ok(())
     }
 }
 
 impl Write for RawFile {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno> {
-        let count = EResult::from(unsafe { syscall::write(self.fd, data) })?;
-        Ok(count)
+    fn write(&mut self, data: &[u8]) -> EResult<usize> {
+        let count = unsafe { syscall::write(self.fd, data) }?;
+        EResult::Ok(count)
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
+    fn flush(&mut self) -> EResult<()> {
         // TODO fsync
-        Ok(())
+        EResult::Ok(())
     }
 }
 
 impl Read for RawFile {
-    fn read(&mut self, data: &mut [u8]) -> Result<usize, Errno> {
-        let count = EResult::from(unsafe { syscall::read(self.fd, data) })?;
-        Ok(count)
+    fn read(&mut self, data: &mut [u8]) -> EResult<usize> {
+        let count = unsafe { syscall::read(self.fd, data) }?;
+        EResult::Ok(count)
     }
 }
 
 impl Seek for RawFile {
-    fn seek(&mut self, off: SeekFrom) -> Result<u64, Errno> {
-        let pos = EResult::from(unsafe { syscall::seek(self.fd, off) })?;
-        Ok(pos)
+    fn seek(&mut self, off: SeekFrom) -> EResult<u64> {
+        let pos = unsafe { syscall::seek(self.fd, off) }?;
+        EResult::Ok(pos)
     }
 }
 
@@ -93,17 +91,10 @@ impl IntoRawFd for RawFile {
     }
 }
 
-impl TryFrom<c_int> for RawFile {
-    type Error = Errno;
-
-    fn try_from(value: c_int) -> Result<Self, Self::Error> {
-        if value >= 0 {
-            Ok(Self {
-                fd: RawFd(value as _),
-            })
-        } else {
-            error::set_errno_result(EBADF)
-        }
+impl TryFromExt<c_int> for RawFile {
+    fn e_try_from(value: c_int) -> EResult<Self> {
+        let fd = RawFd::e_try_from(value)?;
+        EResult::Ok(unsafe { Self::from_raw_fd(fd) })
     }
 }
 
@@ -115,15 +106,15 @@ impl ManagedFile {
         pathname: P,
         opts: OpenOptions,
         mode: FileMode,
-    ) -> Result<Self, Errno> {
+    ) -> EResult<Self> {
         let inner = RawFile::open_at(at, pathname, opts, mode)?;
-        Ok(Self {
+        EResult::Ok(Self {
             inner,
             reference: false,
         })
     }
 
-    pub unsafe fn close(self: &mut Self) -> Result<(), Errno> {
+    pub unsafe fn close(self: &mut Self) -> EResult<()> {
         if self.reference {
             unreachable!("Cannot close a reference ManagedFile");
         }
@@ -183,7 +174,7 @@ impl FileBacking {
         }
     }
 
-    pub unsafe fn close(self: &mut Self) -> Result<(), Errno> {
+    pub unsafe fn close(self: &mut Self) -> EResult<()> {
         match self {
             Self::File(file) => ManagedFile::close(file),
         }
@@ -199,13 +190,13 @@ impl AsRawFdOpt for FileBacking {
 }
 
 impl Write for FileBacking {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno> {
+    fn write(&mut self, data: &[u8]) -> EResult<usize> {
         match self {
             Self::File(file) => file.write(data),
         }
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
+    fn flush(&mut self) -> EResult<()> {
         match self {
             Self::File(file) => file.flush(),
         }
@@ -213,7 +204,7 @@ impl Write for FileBacking {
 }
 
 impl Read for FileBacking {
-    fn read(&mut self, data: &mut [u8]) -> Result<usize, Errno> {
+    fn read(&mut self, data: &mut [u8]) -> EResult<usize> {
         match self {
             Self::File(file) => file.read(data),
         }
@@ -221,7 +212,7 @@ impl Read for FileBacking {
 }
 
 impl Seek for FileBacking {
-    fn seek(&mut self, off: SeekFrom) -> Result<u64, Errno> {
+    fn seek(&mut self, off: SeekFrom) -> EResult<u64> {
         match self {
             Self::File(file) => file.seek(off),
         }
diff --git a/src/header/dirent/mod.rs b/src/header/dirent/mod.rs
index 99c8ae2..7688757 100644
--- a/src/header/dirent/mod.rs
+++ b/src/header/dirent/mod.rs
@@ -1,15 +1,19 @@
 use core::{
     ffi::{c_char, c_int, c_long, CStr},
     mem::MaybeUninit,
-    ptr::null_mut,
+    ptr::NonNull,
 };
 
 use alloc::boxed::Box;
 use yggdrasil_rt::io::{DirectoryEntry, RawFd};
 
-use crate::{error, io::dir::DirReader, util::Nullable};
+use crate::{
+    error::{CIntZeroResult, CPtrResult, EResult, TryFromExt},
+    io::{dir::DirReader, FromRawFd},
+    util::Nullable,
+};
 
-use super::{errno::EBADF, sys_types::ino_t};
+use super::{errno::ESUCCESS, sys_types::ino_t};
 
 #[derive(Debug)]
 #[repr(C)]
@@ -28,6 +32,26 @@ pub struct dirent {
 pub type __scandir_filter_fn_t = extern "C" fn(*const dirent) -> c_int;
 pub type __scandir_compar_fn_t = extern "C" fn(*mut *const dirent, *mut *const dirent) -> c_int;
 
+impl DIR {
+    unsafe fn close(mut dir_ptr: NonNull<Self>) -> EResult<()> {
+        let dir = dir_ptr.as_mut();
+        let result = dir.reader.close();
+        drop(Box::from_raw(dir_ptr.as_ptr()));
+        result
+    }
+
+    fn read_entry(&mut self) -> EResult<NonNull<dirent>> {
+        match self.reader.read_entry() {
+            EResult::Ok(Some(entry)) => {
+                self.buffer.write(dirent::from(entry));
+                EResult::Ok(unsafe { NonNull::new_unchecked(self.buffer.as_mut_ptr()) })
+            }
+            EResult::Ok(None) => EResult::Err(ESUCCESS),
+            EResult::Err(err) => EResult::Err(err),
+        }
+    }
+}
+
 impl From<DirectoryEntry> for dirent {
     fn from(value: DirectoryEntry) -> Self {
         let mut d_name = [0; 256];
@@ -52,49 +76,34 @@ impl From<DirectoryEntry> for dirent {
 // Primary stuff
 
 #[no_mangle]
-unsafe extern "C" fn opendir(pathname: *const c_char) -> *mut DIR {
+unsafe extern "C" fn opendir(pathname: *const c_char) -> CPtrResult<DIR> {
     pathname.ensure();
 
     let pathname = CStr::from_ptr(pathname).to_str().unwrap();
-
-    match DirReader::open_at(None, pathname) {
-        Ok(reader) => Box::into_raw(Box::new(DIR {
-            reader,
-            buffer: MaybeUninit::uninit(),
-        })),
-        Err(_) => null_mut(),
-    }
-}
-
-#[no_mangle]
-unsafe extern "C" fn fdopendir(fd: c_int) -> *mut DIR {
-    if fd < 0 {
-        error::set_errno(EBADF);
-        return null_mut();
-    }
-
-    let reader = DirReader::from_raw_fd(RawFd(fd as _));
-
-    Box::into_raw(Box::new(DIR {
+    let reader = DirReader::open_at(None, pathname)?;
+    let dir = NonNull::from(Box::leak(Box::new(DIR {
         reader,
         buffer: MaybeUninit::uninit(),
-    }))
+    })));
+    CPtrResult::success(dir)
 }
 
 #[no_mangle]
-unsafe extern "C" fn closedir(dir: *mut DIR) -> c_int {
-    let result = {
-        let dir = dir.as_mut().unwrap();
+unsafe extern "C" fn fdopendir(fd: c_int) -> CPtrResult<DIR> {
+    let fd = RawFd::e_try_from(fd)?;
+    let reader = DirReader::from_raw_fd(fd);
+    let dir = NonNull::from(Box::leak(Box::new(DIR {
+        reader,
+        buffer: MaybeUninit::uninit(),
+    })));
+    CPtrResult::success(dir)
+}
 
-        match dir.reader.close() {
-            Ok(_) => 0,
-            Err(_) => -1,
-        }
-    };
-
-    drop(Box::from_raw(dir));
-
-    result
+#[no_mangle]
+unsafe extern "C" fn closedir(dir: *mut DIR) -> CIntZeroResult {
+    let dir = NonNull::new(dir).unwrap();
+    DIR::close(dir)?;
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -105,16 +114,10 @@ unsafe extern "C" fn dirfd(dir: *mut DIR) -> c_int {
 }
 
 #[no_mangle]
-unsafe extern "C" fn readdir(dir: *mut DIR) -> *mut dirent {
+unsafe extern "C" fn readdir(dir: *mut DIR) -> CPtrResult<dirent> {
     let dir = dir.as_mut().unwrap();
-
-    match dir.reader.read_entry() {
-        Ok(Some(entry)) => {
-            dir.buffer.write(dirent::from(entry));
-            dir.buffer.as_mut_ptr()
-        }
-        Ok(None) | Err(_) => null_mut(),
-    }
+    let dirent = dir.read_entry()?;
+    CPtrResult::success(dirent)
 }
 
 // Deprecated
diff --git a/src/header/fcntl/mod.rs b/src/header/fcntl/mod.rs
index 6dd7d46..94a39ab 100644
--- a/src/header/fcntl/mod.rs
+++ b/src/header/fcntl/mod.rs
@@ -2,13 +2,16 @@ use core::ffi::{c_char, c_int, c_short, CStr, VaList};
 
 use yggdrasil_rt::io::{FileMode, OpenOptions};
 
-use crate::{error, file::RawFile, header::errno::EINVAL, io::IntoRawFd, util::Nullable};
-
-use super::{
-    errno::Errno,
-    sys_types::{mode_t, off_t, pid_t},
+use crate::{
+    error::{CFdResult, CIntCountResult, EResult, TryFromExt},
+    file::RawFile,
+    header::errno::EINVAL,
+    io::IntoRawFd,
+    util::{self, Nullable},
 };
 
+use super::sys_types::{mode_t, off_t, pid_t};
+
 /*
 TODO:
 int  posix_fadvise(int, off_t, off_t, int);
@@ -75,13 +78,13 @@ enum OpenMode {
     Directory,
 }
 
-fn open_opts(opts: c_int, ap: &mut VaList) -> Result<OpenMode, Errno> {
+fn open_opts(opts: c_int, ap: &mut VaList) -> EResult<OpenMode> {
     if opts & O_DIRECTORY != 0 {
         if opts & !O_DIRECTORY != 0 {
             todo!();
         }
 
-        return Ok(OpenMode::Directory);
+        return EResult::Ok(OpenMode::Directory);
     }
 
     let need_mode = opts & O_CREAT != 0;
@@ -94,7 +97,7 @@ fn open_opts(opts: c_int, ap: &mut VaList) -> Result<OpenMode, Errno> {
         O_EXEC => todo!(),
         O_SEARCH => todo!(),
         _ => {
-            return error::set_errno_result(EINVAL);
+            return EResult::Err(EINVAL);
         }
     }
 
@@ -124,7 +127,7 @@ fn open_opts(opts: c_int, ap: &mut VaList) -> Result<OpenMode, Errno> {
         FileMode::empty()
     };
 
-    Ok(OpenMode::File(res, mode))
+    EResult::Ok(OpenMode::File(res, mode))
 }
 
 #[no_mangle]
@@ -133,41 +136,38 @@ unsafe extern "C" fn creat(pathname: *const c_char, mode: mode_t) -> c_int {
 }
 
 #[no_mangle]
-unsafe extern "C" fn fcntl(fd: c_int, cmd: c_int, args: ...) -> c_int {
-    let Ok(file) = RawFile::try_from(fd) else {
-        return -1;
-    };
+unsafe extern "C" fn fcntl(fd: c_int, cmd: c_int, args: ...) -> CIntCountResult {
+    let file = RawFile::e_try_from(fd)?;
 
     match cmd {
-        F_GETFD => 0,
-        F_SETFD => 0,
         _ => todo!("fcntl({}, {}, ...)", fd, cmd),
     }
 }
 
-#[no_mangle]
-unsafe extern "C" fn open(pathname: *const c_char, opts: c_int, mut args: ...) -> c_int {
+unsafe fn vopenat(atfd: c_int, pathname: *const c_char, opts: c_int, mut ap: VaList) -> CFdResult {
+    let atfd = util::at_fd(atfd)?;
     pathname.ensure();
     let pathname = CStr::from_ptr(pathname).to_str().unwrap();
-    let mut args = args.as_va_list();
 
-    let result = match open_opts(opts, &mut args) {
-        Ok(OpenMode::File(opts, mode)) => {
-            RawFile::open_at(None, pathname, opts, mode).map(RawFile::into_raw_fd)
-        }
-        Ok(OpenMode::Directory) => {
-            todo!();
-        }
-        Err(_) => return -1,
+    let fd = match open_opts(opts, &mut ap)? {
+        OpenMode::File(opts, mode) => RawFile::open_at(atfd, pathname, opts, mode)?.into_raw_fd(),
+        OpenMode::Directory => todo!(),
     };
 
-    match result {
-        Ok(fd) => fd.0.try_into().unwrap(),
-        Err(_) => -1,
-    }
+    CFdResult::success(fd)
 }
 
 #[no_mangle]
-unsafe extern "C" fn openat(atfd: c_int, pathname: *const c_char, opts: c_int, ...) -> c_int {
-    todo!()
+unsafe extern "C" fn open(pathname: *const c_char, opts: c_int, mut args: ...) -> CFdResult {
+    vopenat(AT_FDCWD, pathname, opts, args.as_va_list())
+}
+
+#[no_mangle]
+unsafe extern "C" fn openat(
+    atfd: c_int,
+    pathname: *const c_char,
+    opts: c_int,
+    mut args: ...
+) -> CFdResult {
+    vopenat(atfd, pathname, opts, args.as_va_list())
 }
diff --git a/src/header/stdio/file.rs b/src/header/stdio/file.rs
index f6fb956..aefca4b 100644
--- a/src/header/stdio/file.rs
+++ b/src/header/stdio/file.rs
@@ -1,6 +1,6 @@
 use core::{
     ffi::{c_char, c_int, c_long, c_void, CStr},
-    ptr::null_mut,
+    ptr::{null_mut, NonNull},
 };
 
 use alloc::boxed::Box;
@@ -10,11 +10,11 @@ use yggdrasil_rt::{
 };
 
 use crate::{
-    error::{self, CSizeResult, CZeroResult},
-    header::{
-        errno::{Errno, EBADF},
-        sys_types::off_t,
+    error::{
+        CEofResult, CFdResult, CIntZeroResult, COffsetResult, CPtrResult, CUsizeResult, EResult,
+        OptionExt,
     },
+    header::{errno::EBADF, sys_types::off_t},
     io::{AsRawFdOpt, Read, Seek, Write},
 };
 
@@ -22,7 +22,7 @@ use super::{
     fpos_t, FileFlags, FileOpenSource, FILE, SEEK_CUR, SEEK_END, SEEK_SET, _IOFBF, _IOLBF, _IONBF,
 };
 
-fn open_inner<O: FileOpenSource>(source: O, mode_str: &[u8]) -> Result<*mut FILE, Errno> {
+fn open_inner<O: FileOpenSource>(source: O, mode_str: &[u8]) -> EResult<NonNull<FILE>> {
     let opts = match mode_str {
         b"r" | b"rb" => OpenOptions::READ,
         b"r+" | b"rb+" => OpenOptions::READ | OpenOptions::WRITE,
@@ -40,16 +40,12 @@ fn open_inner<O: FileOpenSource>(source: O, mode_str: &[u8]) -> Result<*mut FILE
         _ => todo!(),
     };
 
-    match source.open_with(opts) {
-        Ok(file) => {
-            let file = Box::into_raw(Box::new(file));
-            unsafe {
-                super::register_file(file);
-            }
-            Ok(file)
-        }
-        Err(err) => Err(err),
+    let file = source.open_with(opts)?;
+    let file = NonNull::from(Box::leak(Box::new(file)));
+    unsafe {
+        super::register_file(file);
     }
+    EResult::Ok(file)
 }
 
 #[no_mangle]
@@ -58,7 +54,7 @@ pub unsafe extern "C" fn ctermid(buffer: *mut c_char) -> *mut c_char {
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fopen(pathname: *const c_char, mode: *const c_char) -> *mut FILE {
+pub unsafe extern "C" fn fopen(pathname: *const c_char, mode: *const c_char) -> CPtrResult<FILE> {
     if pathname.is_null() || mode.is_null() {
         panic!();
     }
@@ -66,19 +62,21 @@ pub unsafe extern "C" fn fopen(pathname: *const c_char, mode: *const c_char) ->
     let pathname = pathname.to_str().unwrap();
     let mode = CStr::from_ptr(mode);
 
-    let res = open_inner(Path::from_str(pathname), mode.to_bytes()).unwrap_or(null_mut());
-    yggdrasil_rt::debug_trace!("fopen({:?}, {:?}) -> {:p}", pathname, mode, res);
-    res
+    let file = open_inner(Path::from_str(pathname), mode.to_bytes())?;
+
+    CPtrResult::success(file)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fdopen(fd: c_int, mode: *const c_char) -> *mut FILE {
+pub unsafe extern "C" fn fdopen(fd: c_int, mode: *const c_char) -> CPtrResult<FILE> {
     if fd < 0 || mode.is_null() {
         panic!();
     }
     let mode = CStr::from_ptr(mode);
 
-    open_inner(RawFd(fd as u32), mode.to_bytes()).unwrap_or(null_mut())
+    let stream = open_inner(RawFd(fd as u32), mode.to_bytes())?;
+
+    CPtrResult::success(stream)
 }
 
 #[no_mangle]
@@ -109,28 +107,22 @@ pub unsafe extern "C" fn clearerr(stream: *mut FILE) {
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fclose(stream: *mut FILE) -> c_int {
-    if stream.is_null() {
-        panic!();
-    }
+pub unsafe extern "C" fn fclose(stream: *mut FILE) -> CEofResult {
+    let stream = NonNull::new(stream).unwrap();
 
     if !super::deregister_file(stream) {
         yggdrasil_rt::debug_trace!("fclose() non-registered file: {:p}", stream);
     }
 
-    stream.close().into_eof_status()
+    FILE::close(stream)?;
+    CEofResult(0)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fileno(stream: *mut FILE) -> c_int {
+pub unsafe extern "C" fn fileno(stream: *mut FILE) -> CFdResult {
     let stream = stream.as_mut().unwrap();
-    match stream.as_raw_fd_opt() {
-        Some(RawFd(fd)) => fd as _,
-        None => {
-            error::set_errno(EBADF);
-            -1
-        }
-    }
+    let fd = stream.as_raw_fd_opt().e_ok_or(EBADF)?;
+    CFdResult::success(fd)
 }
 
 #[no_mangle]
@@ -139,14 +131,15 @@ pub unsafe extern "C" fn fwrite(
     size: usize,
     nmemb: usize,
     stream: *mut FILE,
-) -> usize {
+) -> CUsizeResult {
     if ptr.is_null() {
         panic!();
     }
     let stream = stream.as_mut().unwrap();
     let data = core::slice::from_raw_parts(ptr as *const u8, size * nmemb);
 
-    stream.write(data).into_size_status() / size
+    let count = stream.write(data)?;
+    CUsizeResult(count / size)
 }
 
 #[no_mangle]
@@ -155,32 +148,35 @@ pub unsafe extern "C" fn fread(
     size: usize,
     nmemb: usize,
     stream: *mut FILE,
-) -> usize {
+) -> CUsizeResult {
     if ptr.is_null() {
         panic!();
     }
     let stream = stream.as_mut().unwrap();
     let data = core::slice::from_raw_parts_mut(ptr as *mut u8, size * nmemb);
 
-    stream.read(data).into_size_status() / size
+    let count = stream.read(data)?;
+    CUsizeResult(count / size)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fflush(stream: *mut FILE) -> c_int {
+pub unsafe extern "C" fn fflush(stream: *mut FILE) -> CEofResult {
     if let Some(stream) = stream.as_mut() {
-        stream.flush().into_eof_status()
+        stream.flush()?;
     } else {
-        super::fflush_all().into_eof_status()
+        super::fflush_all()?;
     }
+
+    CEofResult(0)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fseek(stream: *mut FILE, offset: c_long, whence: c_int) -> c_int {
+pub unsafe extern "C" fn fseek(stream: *mut FILE, offset: c_long, whence: c_int) -> CIntZeroResult {
     fseeko(stream, offset.try_into().unwrap(), whence)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fseeko(stream: *mut FILE, offset: off_t, whence: c_int) -> c_int {
+pub unsafe extern "C" fn fseeko(stream: *mut FILE, offset: off_t, whence: c_int) -> CIntZeroResult {
     let stream = stream.as_mut().unwrap();
     let off = match whence {
         SEEK_SET => SeekFrom::Start(offset.try_into().unwrap()),
@@ -190,24 +186,24 @@ pub unsafe extern "C" fn fseeko(stream: *mut FILE, offset: off_t, whence: c_int)
         _ => todo!(),
     };
 
-    match stream.seek(off) {
-        Ok(_) => 0,
-        Err(_) => -1,
-    }
+    stream.seek(off)?;
+
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn ftell(stream: *mut FILE) -> c_long {
-    ftello(stream).try_into().unwrap()
+    match ftello(stream).ok() {
+        Some(off) => off,
+        None => -1,
+    }
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn ftello(stream: *mut FILE) -> off_t {
+pub unsafe extern "C" fn ftello(stream: *mut FILE) -> COffsetResult {
     let stream = stream.as_mut().unwrap();
-    match stream.stream_position() {
-        Ok(p) => p.try_into().unwrap(),
-        Err(_) => -1,
-    }
+    let pos = stream.stream_position()?;
+    COffsetResult::success(pos)
 }
 
 #[no_mangle]
@@ -216,26 +212,20 @@ pub unsafe extern "C" fn rewind(stream: *mut FILE) {
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fgetpos(stream: *mut FILE, pos: *mut fpos_t) -> c_int {
+pub unsafe extern "C" fn fgetpos(stream: *mut FILE, pos: *mut fpos_t) -> CIntZeroResult {
     let stream = stream.as_mut().unwrap();
-    let pos = pos.as_mut().unwrap();
-    match stream.stream_position() {
-        Ok(p) => {
-            *pos = p;
-            0
-        }
-        Err(_) => -1,
-    }
+    let dst = pos.as_mut().unwrap();
+    let pos = stream.stream_position()?;
+    *dst = pos;
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fsetpos(stream: *mut FILE, pos: *const fpos_t) -> c_int {
+pub unsafe extern "C" fn fsetpos(stream: *mut FILE, pos: *const fpos_t) -> CIntZeroResult {
     let stream = stream.as_mut().unwrap();
     let pos = pos.as_ref().unwrap();
-    match stream.seek(SeekFrom::Start(*pos as _)) {
-        Ok(_) => 0,
-        Err(_) => -1,
-    }
+    stream.seek(SeekFrom::Start(*pos))?;
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -244,9 +234,10 @@ pub unsafe extern "C" fn setvbuf(
     buf: *mut c_char,
     mode: c_int,
     size: usize,
-) -> c_int {
+) -> CIntZeroResult {
     let stream = stream.as_mut().unwrap();
-    stream.setvbuf(mode, buf, size).into_eof_status()
+    stream.setvbuf(mode, buf, size)?;
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -266,17 +257,24 @@ pub unsafe extern "C" fn setlinebuf(stream: *mut FILE) {
 }
 
 #[no_mangle]
-unsafe extern "C" fn fmemopen(buffer: *mut c_void, size: usize, mode: *mut c_char) -> *mut FILE {
+unsafe extern "C" fn fmemopen(
+    buffer: *mut c_void,
+    size: usize,
+    mode: *mut c_char,
+) -> CPtrResult<FILE> {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn open_memstream(bufptr: *mut *mut c_char, sizeptr: *mut usize) -> *mut FILE {
+unsafe extern "C" fn open_memstream(
+    bufptr: *mut *mut c_char,
+    sizeptr: *mut usize,
+) -> CPtrResult<FILE> {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn popen(command: *const c_char, mode: *const c_char) -> *mut FILE {
+unsafe extern "C" fn popen(command: *const c_char, mode: *const c_char) -> CPtrResult<FILE> {
     todo!()
 }
 
diff --git a/src/header/stdio/get_put.rs b/src/header/stdio/get_put.rs
index 25f7a36..b05e92f 100644
--- a/src/header/stdio/get_put.rs
+++ b/src/header/stdio/get_put.rs
@@ -1,18 +1,20 @@
 use core::{
     ffi::{c_char, c_int, CStr},
-    ptr::null_mut,
+    ptr::{null_mut, NonNull},
 };
 
 use crate::{
-    error,
-    header::stdlib::realloc,
+    allocator,
+    error::{self, CEofResult, CIsizeResult, CPtrResult, EResult},
+    header::errno::ESUCCESS,
     io::{Read, Write},
+    util::NonNullExt,
 };
 
 use super::{
     stderr, stdin, stdout,
     unlocked::{flockfile, fputc_unlocked, fputs_unlocked, funlockfile},
-    EOF, FILE,
+    FILE,
 };
 
 #[no_mangle]
@@ -34,101 +36,91 @@ unsafe extern "C" fn perror(msg: *const c_char) {
 // Chars
 
 #[no_mangle]
-unsafe extern "C" fn fputc(c: c_int, stream: *mut FILE) -> c_int {
+unsafe extern "C" fn fputc(c: c_int, stream: *mut FILE) -> CEofResult {
     let stream = stream.as_mut().unwrap();
     let c = c as u8;
 
-    match stream.write(&[c]) {
-        Ok(_) => c as c_int,
-        Err(_) => EOF,
-    }
+    stream.write_all(&[c])?;
+
+    CEofResult(c as c_int)
 }
 
 #[no_mangle]
-unsafe extern "C" fn putc(c: c_int, stream: *mut FILE) -> c_int {
+unsafe extern "C" fn putc(c: c_int, stream: *mut FILE) -> CEofResult {
     fputc(c, stream)
 }
 
 #[no_mangle]
-unsafe extern "C" fn putchar(c: c_int) -> c_int {
+unsafe extern "C" fn putchar(c: c_int) -> CEofResult {
     fputc(c, stdout)
 }
 
 // Strings
 
 #[no_mangle]
-unsafe extern "C" fn puts(s: *const c_char) -> c_int {
+unsafe extern "C" fn puts(s: *const c_char) -> CEofResult {
     let r = fputs(s, stdout);
-    if r < 0 {
+    if r.0 < 0 {
         return r;
     }
     fputc(b'\n' as _, stdout)
 }
 
 #[no_mangle]
-unsafe extern "C" fn fputs(s: *const c_char, stream: *mut FILE) -> c_int {
+unsafe extern "C" fn fputs(s: *const c_char, stream: *mut FILE) -> CEofResult {
     let stream = stream.as_mut().unwrap();
     if s.is_null() {
         panic!();
     }
     let s = CStr::from_ptr(s);
-
-    match stream.write(s.to_bytes()) {
-        Ok(_) => 0,
-        Err(_) => EOF,
-    }
+    stream.write_all(s.to_bytes())?;
+    CEofResult(0)
 }
 
 #[no_mangle]
-unsafe extern "C" fn fgetc(stream: *mut FILE) -> c_int {
+unsafe extern "C" fn fgetc(stream: *mut FILE) -> CEofResult {
     let stream = stream.as_mut().unwrap();
     let mut buf = [0];
-    match stream.read(&mut buf) {
-        Ok(1) => buf[0] as c_int,
-        Ok(_) => EOF,
-        Err(_) => EOF,
-    }
+    stream.read_exact(&mut buf)?;
+    CEofResult(buf[0] as _)
 }
 
 #[no_mangle]
-unsafe extern "C" fn getc(stream: *mut FILE) -> c_int {
+unsafe extern "C" fn getc(stream: *mut FILE) -> CEofResult {
     fgetc(stream)
 }
 
 #[no_mangle]
-unsafe extern "C" fn getchar() -> c_int {
+unsafe extern "C" fn getchar() -> CEofResult {
     fgetc(stdin)
 }
 
 #[no_mangle]
-unsafe extern "C" fn fgets(s: *mut c_char, size: c_int, stream: *mut FILE) -> *mut c_char {
+unsafe extern "C" fn fgets(s: *mut c_char, size: c_int, stream: *mut FILE) -> CPtrResult<c_char> {
     let stream = stream.as_mut().unwrap();
+    let mut s = NonNull::new(s).unwrap();
 
     if size <= 0 {
-        return null_mut();
+        return CPtrResult::ERR;
     }
     // Nothing to read
     if size == 1 {
-        *s = 0;
-        return s;
+        *s.as_mut() = 0;
+        return CPtrResult::success(s);
     }
 
     let size = size as usize;
     let mut pos = 0;
     let mut buf = [0];
+    let slice = NonNull::slice_from_raw_parts(s, size).as_mut();
 
     while pos < size - 1 {
-        let ch = match stream.read(&mut buf) {
-            Ok(1) => buf[0],
-            Ok(_) => {
-                break;
-            }
-            Err(err) => {
-                return null_mut();
-            }
+        let ch = match stream.read(&mut buf)? {
+            1 => buf[0],
+            _ => break,
         };
 
-        *s.add(pos) = ch as _;
+        slice[pos] = ch as _;
         pos += 1;
 
         if ch == b'\n' {
@@ -137,49 +129,101 @@ unsafe extern "C" fn fgets(s: *mut c_char, size: c_int, stream: *mut FILE) -> *m
     }
 
     if pos == 0 {
-        null_mut()
+        CPtrResult::ERR
     } else {
-        *s.add(pos) = 0;
-        s
+        slice[pos] = 0;
+        CPtrResult::success(s)
     }
 }
 
 #[no_mangle]
-unsafe extern "C" fn ungetc(c: c_int, stream: *mut FILE) -> c_int {
+unsafe extern "C" fn ungetc(c: c_int, stream: *mut FILE) -> CEofResult {
     let stream = stream.as_mut().unwrap();
-    if stream.ungetc(c as _) {
-        c
-    } else {
-        EOF
-    }
+    stream.ungetc(c as _)?;
+    CEofResult(c)
 }
 
 // Line
 
 struct MallocBufferWriter {
-    buffer: *mut c_char,
-    position: usize,
+    buffer: Option<NonNull<c_char>>,
     capacity: usize,
+    position: usize,
 }
 
 impl MallocBufferWriter {
-    fn putc(&mut self, ch: c_int) -> bool {
+    unsafe fn new(buffer: Option<NonNull<c_char>>, mut capacity: usize) -> Self {
+        if buffer.is_none() {
+            capacity = 0;
+        }
+        Self {
+            buffer,
+            capacity,
+            position: 0,
+        }
+    }
+
+    fn try_reserve(&mut self) -> EResult<&mut c_char> {
         if self.position == self.capacity {
-            // Extend the buffer
             self.capacity = (self.capacity + 64) & !63;
-            self.buffer = unsafe { realloc(self.buffer as _, self.capacity) as _ };
-            if self.buffer.is_null() {
-                // ENOMEM is set
-                return false;
+            self.buffer = Some(
+                unsafe { allocator::c_reallocate(self.buffer.map(NonNull::cast), self.capacity) }?
+                    .cast(),
+            );
+        }
+        let buffer = self.buffer.unwrap();
+        EResult::Ok(unsafe { buffer.add_ext(self.position).as_mut() })
+    }
+
+    fn putc(&mut self, ch: c_int) -> EResult<()> {
+        let item = self.try_reserve()?;
+        *item = ch as _;
+        self.position += 1;
+        EResult::Ok(())
+    }
+}
+
+fn getdelim_inner(
+    buffer: Option<NonNull<c_char>>,
+    capacity: usize,
+    delim: c_int,
+    stream: &mut FILE,
+) -> (MallocBufferWriter, EResult<()>) {
+    let mut writer = unsafe { MallocBufferWriter::new(buffer, capacity) };
+    let mut buf = [0];
+
+    loop {
+        let ch = match stream.read(&mut buf) {
+            EResult::Ok(1) => buf[0] as c_int,
+            EResult::Ok(_) => break,
+            EResult::Err(err) => return (writer, EResult::Err(err)),
+        };
+
+        match writer.putc(ch) {
+            EResult::Ok(()) => (),
+            EResult::Err(err) => {
+                return (writer, EResult::Err(err));
             }
         }
 
-        unsafe {
-            *self.buffer.add(self.position) = ch as _;
+        if ch == delim {
+            break;
         }
-        self.position += 1;
-        true
     }
+
+    if writer.position == 0 {
+        // EOF reached before anything could be read
+        return (writer, EResult::Err(ESUCCESS));
+    }
+
+    match writer.putc(0) {
+        EResult::Ok(()) => (),
+        EResult::Err(err) => {
+            return (writer, EResult::Err(err));
+        }
+    }
+
+    (writer, EResult::Ok(()))
 }
 
 #[no_mangle]
@@ -188,52 +232,32 @@ unsafe extern "C" fn getdelim(
     n: *mut usize,
     delim: c_int,
     stream: *mut FILE,
-) -> isize {
+) -> CIsizeResult {
     let lineptr = lineptr.as_mut().unwrap();
+
+    let buffer = NonNull::new(*lineptr);
     let n = n.as_mut().unwrap();
-    let mut capacity = *n;
+    let stream = stream.as_mut().unwrap();
 
-    if lineptr.is_null() {
-        capacity = 0;
+    let (writer, result) = getdelim_inner(buffer, *n, delim, stream);
+
+    match writer.buffer {
+        Some(buffer) => *lineptr = buffer.as_ptr(),
+        None => *lineptr = null_mut(),
     }
-
-    let mut writer = MallocBufferWriter {
-        buffer: *lineptr,
-        position: 0,
-        capacity,
-    };
-
-    loop {
-        let ch = fgetc(stream);
-        if ch == EOF {
-            if writer.position == 0 {
-                // EOF and no data read
-                return -1;
-            }
-            break;
-        }
-
-        if !writer.putc(ch) {
-            return -1;
-        }
-
-        if ch == delim {
-            break;
-        }
-    }
-
-    if !writer.putc(0) {
-        return -1;
-    }
-
-    *lineptr = writer.buffer;
     *n = writer.capacity;
 
-    // Minus the '\0'
-    (writer.position - 1).try_into().unwrap()
+    result?;
+    assert_ne!(writer.position, 0);
+
+    CIsizeResult::success(writer.position - 1)
 }
 
 #[no_mangle]
-unsafe extern "C" fn getline(lineptr: *mut *mut c_char, n: *mut usize, stream: *mut FILE) -> isize {
+unsafe extern "C" fn getline(
+    lineptr: *mut *mut c_char,
+    n: *mut usize,
+    stream: *mut FILE,
+) -> CIsizeResult {
     getdelim(lineptr, n, b'\n' as _, stream)
 }
diff --git a/src/header/stdio/mod.rs b/src/header/stdio/mod.rs
index ac7fcb6..7db94ef 100644
--- a/src/header/stdio/mod.rs
+++ b/src/header/stdio/mod.rs
@@ -1,6 +1,7 @@
 use core::{
     ffi::{c_char, c_int},
-    fmt, ptr,
+    fmt,
+    ptr::{self, NonNull},
 };
 
 use alloc::{boxed::Box, collections::BTreeSet, vec::Vec};
@@ -20,7 +21,7 @@ use crate::{
     sync::{Mutex, RawMutex},
 };
 
-use super::errno::Errno;
+use super::errno::{EINVAL, ENOMEM, ESUCCESS};
 
 // TODO:
 // L_ctermid
@@ -42,7 +43,7 @@ mod scanf;
 mod unlocked;
 
 pub trait FileOpenSource {
-    fn open_with(self, opts: OpenOptions) -> Result<FILE, Errno>;
+    fn open_with(self, opts: OpenOptions) -> EResult<FILE>;
 }
 
 pub enum BufferingMode {
@@ -126,16 +127,16 @@ impl FILE {
         Self::from_backing(inner, flags, buffering)
     }
 
-    pub unsafe fn close(self: *mut Self) -> Result<(), Errno> {
+    pub unsafe fn close(mut ptr: NonNull<Self>) -> EResult<()> {
         // TODO lock needed?
-        let r = self.as_mut().unwrap();
-        r.flush()?;
+        let file = ptr.as_mut();
+        file.flush()?;
 
-        if r.flags.contains(FileFlags::BUILTIN) {
+        if file.flags.contains(FileFlags::BUILTIN) {
             todo!()
         } else {
             // Drop the file
-            let mut this = Box::from_raw(self);
+            let mut this = Box::from_raw(file);
             let result = FileBacking::close(&mut this.inner);
             drop(this);
             result
@@ -162,41 +163,36 @@ impl FILE {
         self.flags.contains(flag)
     }
 
-    pub fn setvbuf(
-        &mut self,
-        mode: c_int,
-        buffer: *mut c_char,
-        capacity: usize,
-    ) -> Result<(), Errno> {
+    pub fn setvbuf(&mut self, mode: c_int, buffer: *mut c_char, capacity: usize) -> EResult<()> {
         locked_op!(self, self.setvbuf_unlocked(mode, buffer, capacity))
     }
 
-    pub unsafe fn write_unlocked(&mut self, data: &[u8]) -> Result<usize, Errno> {
+    pub unsafe fn write_unlocked(&mut self, data: &[u8]) -> EResult<usize> {
         self.set_direction(Direction::Write)?;
 
         match self.output.write(data) {
-            Ok(amount) => Ok(amount),
-            Err(err) => {
+            EResult::Ok(amount) => EResult::Ok(amount),
+            EResult::Err(err) => {
                 self.flags |= FileFlags::ERROR;
-                Err(err)
+                EResult::Err(err)
             }
         }
     }
 
-    pub unsafe fn flush_unlocked(&mut self) -> Result<(), Errno> {
+    pub unsafe fn flush_unlocked(&mut self) -> EResult<()> {
         match self.output.flush() {
-            Ok(()) => {
+            EResult::Ok(()) => {
                 self.last_operation = None;
-                Ok(())
+                EResult::Ok(())
             }
-            Err(err) => {
+            EResult::Err(err) => {
                 self.flags |= FileFlags::ERROR;
-                Err(err)
+                EResult::Err(err)
             }
         }
     }
 
-    pub unsafe fn read_unlocked(&mut self, data: &mut [u8]) -> Result<usize, Errno> {
+    pub unsafe fn read_unlocked(&mut self, data: &mut [u8]) -> EResult<usize> {
         self.set_direction(Direction::Read)?;
 
         if !self.ungetc.is_empty() {
@@ -204,7 +200,7 @@ impl FILE {
             let amount = core::cmp::min(self.ungetc.len(), data.len());
             data[..amount].copy_from_slice(&self.ungetc[..amount]);
             self.ungetc.drain(..amount);
-            return Ok(amount);
+            return EResult::Ok(amount);
         }
 
         if self.read_buffer.is_some() {
@@ -212,23 +208,23 @@ impl FILE {
             let len = core::cmp::min(data.len(), buf.len());
             data[..len].copy_from_slice(&buf[..len]);
             self.consume(len);
-            Ok(len)
+            EResult::Ok(len)
         } else {
             match self.inner.read(data) {
-                Ok(0) => {
+                EResult::Ok(0) => {
                     self.flags |= FileFlags::EOF;
-                    Ok(0)
+                    EResult::Ok(0)
                 }
-                Ok(n) => Ok(n),
-                Err(err) => {
+                EResult::Ok(n) => EResult::Ok(n),
+                EResult::Err(err) => {
                     self.flags |= FileFlags::ERROR;
-                    Err(err)
+                    EResult::Err(err)
                 }
             }
         }
     }
 
-    pub fn ungetc(&mut self, ch: u8) -> bool {
+    pub fn ungetc(&mut self, ch: u8) -> EResult<()> {
         locked_op!(self, self.ungetc_unlocked(ch))
     }
 
@@ -236,8 +232,11 @@ impl FILE {
         self.lock.lock();
     }
 
-    pub fn try_lock(&mut self) -> bool {
-        self.lock.try_lock()
+    pub fn try_lock(&mut self) -> EResult<()> {
+        match self.lock.try_lock() {
+            true => EResult::Ok(()),
+            false => EResult::Err(ESUCCESS),
+        }
     }
 
     pub unsafe fn unlock(&mut self) {
@@ -259,7 +258,7 @@ impl FILE {
         mode: c_int,
         buffer: *mut c_char,
         capacity: usize,
-    ) -> Result<(), Errno> {
+    ) -> EResult<()> {
         let mode = BufferingMode::e_try_from(mode)?;
 
         if self.last_operation.is_some() {
@@ -306,84 +305,83 @@ impl FILE {
             }
         }
 
-        Ok(())
+        EResult::Ok(())
     }
 
-    unsafe fn seek_unlocked(&mut self, off: SeekFrom) -> Result<u64, Errno> {
+    unsafe fn seek_unlocked(&mut self, off: SeekFrom) -> EResult<u64> {
         self.flush_unlocked()?;
         self.ungetc.clear();
 
         match self.inner.seek(off) {
-            Ok(pos) => {
+            EResult::Ok(pos) => {
                 self.flags &= !FileFlags::EOF;
-                Ok(pos)
+                EResult::Ok(pos)
             }
-            Err(err) => {
+            EResult::Err(err) => {
                 self.flags |= FileFlags::ERROR;
-                Err(err)
+                EResult::Err(err)
             }
         }
     }
 
-    unsafe fn set_direction(&mut self, direction: Direction) -> Result<(), Errno> {
+    unsafe fn set_direction(&mut self, direction: Direction) -> EResult<()> {
         match self.last_operation.replace(direction) {
             Some(dir) if dir != direction => {
                 self.flags |= FileFlags::ERROR;
                 todo!()
             }
-            _ => Ok(()),
+            _ => EResult::Ok(()),
         }
     }
 
-    unsafe fn ungetc_unlocked(&mut self, ch: u8) -> bool {
+    unsafe fn ungetc_unlocked(&mut self, ch: u8) -> EResult<()> {
         // ungetc() for write doesn't make any sense
-        if self.set_direction(Direction::Read).is_err() {
-            return false;
-        }
+        self.set_direction(Direction::Read)?;
         if self.ungetc.len() == UNGETC_MAX {
-            return false;
+            return EResult::Err(ENOMEM);
         }
         self.ungetc.push(ch);
-        true
+        EResult::Ok(())
     }
 }
 
 impl fmt::Write for FILE {
     fn write_str(&mut self, s: &str) -> fmt::Result {
-        self.write_all(s.as_bytes()).map_err(|_| fmt::Error)
+        self.write_all(s.as_bytes())
+            .into_result(|_| fmt::Error, true)
     }
 }
 
 impl Write for FILE {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno> {
+    fn write(&mut self, data: &[u8]) -> EResult<usize> {
         locked_op!(self, self.write_unlocked(data))
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
+    fn flush(&mut self) -> EResult<()> {
         locked_op!(self, self.flush_unlocked())
     }
 }
 
 impl Read for FILE {
-    fn read(&mut self, data: &mut [u8]) -> Result<usize, Errno> {
+    fn read(&mut self, data: &mut [u8]) -> EResult<usize> {
         locked_op!(self, self.read_unlocked(data))
     }
 }
 
 // NOTE assumes file is locked
 impl BufRead for FILE {
-    fn fill_buf(&mut self) -> Result<&[u8], Errno> {
+    fn fill_buf(&mut self) -> EResult<&[u8]> {
         let buffer = self.read_buffer.as_mut().unwrap();
         match buffer.fill_from(&mut self.inner) {
-            Ok(slice) => {
+            EResult::Ok(slice) => {
                 if slice.len() == 0 {
                     self.flags |= FileFlags::EOF;
                 }
-                Ok(slice)
+                EResult::Ok(slice)
             }
-            Err(err) => {
+            EResult::Err(err) => {
                 self.flags |= FileFlags::ERROR;
-                Err(err)
+                EResult::Err(err)
             }
         }
     }
@@ -395,7 +393,7 @@ impl BufRead for FILE {
 }
 
 impl Seek for FILE {
-    fn seek(&mut self, off: SeekFrom) -> Result<u64, Errno> {
+    fn seek(&mut self, off: SeekFrom) -> EResult<u64> {
         locked_op!(self, self.seek_unlocked(off))
     }
 }
@@ -407,7 +405,7 @@ impl AsRawFdOpt for FILE {
 }
 
 impl FileOpenSource for &Path {
-    fn open_with(self, opts: OpenOptions) -> Result<FILE, Errno> {
+    fn open_with(self, opts: OpenOptions) -> EResult<FILE> {
         let f = ManagedFile::open_at(None, self, opts, FileMode::default_file())?;
         let mut flags = FileFlags::empty();
         if opts.contains(OpenOptions::READ) {
@@ -416,12 +414,12 @@ impl FileOpenSource for &Path {
         if opts.contains(OpenOptions::WRITE) {
             flags |= FileFlags::WRITE;
         }
-        Ok(unsafe { FILE::from_managed_file(f, flags) })
+        EResult::Ok(unsafe { FILE::from_managed_file(f, flags) })
     }
 }
 
 impl FileOpenSource for RawFd {
-    fn open_with(self, opts: OpenOptions) -> Result<FILE, Errno> {
+    fn open_with(self, opts: OpenOptions) -> EResult<FILE> {
         let f = unsafe { RawFile::from_raw_fd(self) };
         let mut flags = FileFlags::empty();
         if opts.contains(OpenOptions::READ) {
@@ -430,7 +428,7 @@ impl FileOpenSource for RawFd {
         if opts.contains(OpenOptions::WRITE) {
             flags |= FileFlags::WRITE;
         }
-        Ok(unsafe { FILE::from_raw_file(f, flags) })
+        EResult::Ok(unsafe { FILE::from_raw_file(f, flags) })
     }
 }
 
@@ -440,7 +438,7 @@ impl TryFromExt<c_int> for BufferingMode {
             _IOFBF => EResult::Ok(Self::Full),
             _IOLBF => EResult::Ok(Self::Line),
             _IONBF => EResult::Ok(Self::None),
-            _ => EResult::Err(yggdrasil_rt::Error::InvalidArgument),
+            _ => EResult::Err(EINVAL),
         }
     }
 }
@@ -470,28 +468,28 @@ pub const BUFSIZ: usize = 8192;
 
 const UNGETC_MAX: usize = 128;
 
-pub static OPEN_FILES: Mutex<BTreeSet<*mut FILE>> = Mutex::new(BTreeSet::new());
+pub static OPEN_FILES: Mutex<BTreeSet<NonNull<FILE>>> = Mutex::new(BTreeSet::new());
 
-pub unsafe fn register_file(file: *mut FILE) {
+pub unsafe fn register_file(file: NonNull<FILE>) {
     OPEN_FILES.lock().insert(file);
 }
 
-pub unsafe fn deregister_file(file: *mut FILE) -> bool {
+pub unsafe fn deregister_file(file: NonNull<FILE>) -> bool {
     OPEN_FILES.lock().remove(&file)
 }
 
 pub unsafe fn setup_default_files() {
-    let stdin_ = Box::into_raw(Box::new(FILE::new_builtin(
+    let stdin_ = Box::leak(Box::new(FILE::new_builtin(
         RawFd::STDIN,
         FileFlags::READ,
         BufferingMode::Line,
     )));
-    let stdout_ = Box::into_raw(Box::new(FILE::new_builtin(
+    let stdout_ = Box::leak(Box::new(FILE::new_builtin(
         RawFd::STDOUT,
         FileFlags::WRITE,
         BufferingMode::Line,
     )));
-    let stderr_ = Box::into_raw(Box::new(FILE::new_builtin(
+    let stderr_ = Box::leak(Box::new(FILE::new_builtin(
         RawFd::STDERR,
         FileFlags::WRITE,
         BufferingMode::None,
@@ -502,32 +500,34 @@ pub unsafe fn setup_default_files() {
     stderr = stderr_;
 
     let mut open_files = OPEN_FILES.lock();
-    open_files.insert(stdin);
-    open_files.insert(stdout);
-    open_files.insert(stderr);
+    open_files.insert(NonNull::from(stdin_));
+    open_files.insert(NonNull::from(stdout_));
+    open_files.insert(NonNull::from(stderr_));
 }
 
-pub fn fflush_all() -> Result<(), Errno> {
+pub fn fflush_all() -> EResult<()> {
     let open_files = OPEN_FILES.lock();
-    for &file in open_files.iter() {
+    for file in open_files.iter() {
+        let mut file = *file;
         unsafe {
-            file.as_mut().unwrap().flush()?;
+            file.as_mut().flush()?;
         }
     }
-    Ok(())
+    EResult::Ok(())
 }
 
-pub unsafe fn fflush_all_unlocked() -> Result<(), Errno> {
+pub unsafe fn fflush_all_unlocked() -> EResult<()> {
     let open_files = OPEN_FILES.lock();
-    for &file in open_files.iter() {
-        file.as_mut().unwrap().flush_unlocked()?;
+    for file in open_files.iter() {
+        let mut file = *file;
+        file.as_mut().flush_unlocked()?;
     }
-    Ok(())
+    EResult::Ok(())
 }
 
 pub unsafe fn cleanup() {
     let mut open_files = OPEN_FILES.lock();
     while let Some(file) = open_files.pop_first() {
-        file.close().ok();
+        FILE::close(file).ok();
     }
 }
diff --git a/src/header/stdio/printf/float.rs b/src/header/stdio/printf/float.rs
index 7dc3520..97fe922 100644
--- a/src/header/stdio/printf/float.rs
+++ b/src/header/stdio/printf/float.rs
@@ -2,10 +2,7 @@ use core::{ffi::c_double, fmt, num::FpCategory};
 
 use alloc::{format, string::String};
 
-use crate::{
-    header::errno::{Errno, EINVAL},
-    io::Write,
-};
+use crate::{error::EResult, header::errno::EINVAL, io::Write};
 
 use super::format::FmtOpts;
 
@@ -37,7 +34,7 @@ fn fmt_float_exp<W: Write + fmt::Write>(
     output: &mut W,
     precision: usize,
     opts: &FmtOpts,
-) -> Result<usize, Errno> {
+) -> EResult<usize> {
     let mut exp2 = exp;
     let mut exp_len = 1;
     while exp2 >= 10 {
@@ -48,12 +45,14 @@ fn fmt_float_exp<W: Write + fmt::Write>(
     let string = fmt_float_string(val, precision);
 
     let f_len = output.write(string.as_bytes())?;
+
     let e_len = match write!(output, "{}{:+03}", exp_fmt as char, exp) {
         Ok(count) => count,
-        Err(_) => return Err(EINVAL),
+        // TODO proper error code
+        Err(_) => return EResult::Err(EINVAL),
     };
 
-    Ok(f_len + 2 + 2.max(exp_len))
+    EResult::Ok(f_len + 2 + 2.max(exp_len))
 }
 
 fn fmt_float_string(val: c_double, precision: usize) -> String {
@@ -67,12 +66,12 @@ fn fmt_float_finite<W: Write + fmt::Write>(
     output: &mut W,
     precision: usize,
     opts: &FmtOpts,
-) -> Result<usize, Errno> {
+) -> EResult<usize> {
     let s = fmt_float_string(val, precision);
     let lpad = opts.left_pad(output, s.len())?;
     let flen = output.write(s.as_bytes())?;
     let rpad = opts.right_pad(output, s.len())?;
-    Ok(lpad + flen + rpad)
+    EResult::Ok(lpad + flen + rpad)
 }
 
 fn fmt_float_nonfinite<W: Write + fmt::Write>(
@@ -80,7 +79,7 @@ fn fmt_float_nonfinite<W: Write + fmt::Write>(
     output: &mut W,
     upper: bool,
     opts: &FmtOpts,
-) -> Result<usize, Errno> {
+) -> EResult<usize> {
     let mut len = 0;
     if val.is_sign_negative() {
         len += output.write(b"-")?;
@@ -102,7 +101,7 @@ fn fmt_float_nonfinite<W: Write + fmt::Write>(
     let flen = output.write(nonfinite_str)?;
     let rpad = opts.right_pad(output, len + nonfinite_str.len())?;
 
-    Ok(len + lpad + flen + rpad)
+    EResult::Ok(len + lpad + flen + rpad)
 }
 
 pub fn fmt_float<W: Write + fmt::Write>(
@@ -110,7 +109,7 @@ pub fn fmt_float<W: Write + fmt::Write>(
     output: &mut W,
     upper: bool,
     opts: &FmtOpts,
-) -> Result<usize, Errno> {
+) -> EResult<usize> {
     if val.is_finite() {
         fmt_float_finite(val, output, 6, opts)
     } else {
@@ -123,7 +122,7 @@ pub fn fmt_float_scientific<W: Write + fmt::Write>(
     output: &mut W,
     upper: bool,
     opts: &FmtOpts,
-) -> Result<usize, Errno> {
+) -> EResult<usize> {
     if val.is_finite() {
         let (val, exp) = float_exp(val);
         let exp_fmt = match upper {
@@ -143,7 +142,7 @@ pub fn fmt_float_any<W: Write + fmt::Write>(
     output: &mut W,
     upper: bool,
     opts: &FmtOpts,
-) -> Result<usize, Errno> {
+) -> EResult<usize> {
     if val.is_finite() {
         let (log, exp) = float_exp(val);
         let exp_fmt = match upper {
diff --git a/src/header/stdio/printf/format.rs b/src/header/stdio/printf/format.rs
index 1190f89..0018430 100644
--- a/src/header/stdio/printf/format.rs
+++ b/src/header/stdio/printf/format.rs
@@ -8,7 +8,7 @@ use core::{
 
 use alloc::string::String;
 
-use crate::{header::errno::Errno, io::Write, types::wchar_t};
+use crate::{error::EResult, io::Write, types::wchar_t};
 
 use super::float::{fmt_float, fmt_float_any, fmt_float_scientific};
 
@@ -144,35 +144,27 @@ impl FmtSize {
 }
 
 impl FmtOpts {
-    fn pad<W: Write + fmt::Write>(&self, output: &mut W, len: usize) -> Result<usize, Errno> {
+    fn pad<W: Write + fmt::Write>(&self, output: &mut W, len: usize) -> EResult<usize> {
         let pad = self.width - core::cmp::min(self.width, len);
         for _ in 0..pad {
             output.write(&[self.pad_char])?;
         }
-        Ok(pad)
+        EResult::Ok(pad)
     }
 
-    pub fn left_pad<W: Write + fmt::Write>(
-        &self,
-        output: &mut W,
-        len: usize,
-    ) -> Result<usize, Errno> {
+    pub fn left_pad<W: Write + fmt::Write>(&self, output: &mut W, len: usize) -> EResult<usize> {
         if !self.left_adjust {
             self.pad(output, len)
         } else {
-            Ok(0)
+            EResult::Ok(0)
         }
     }
 
-    pub fn right_pad<W: Write + fmt::Write>(
-        &self,
-        output: &mut W,
-        len: usize,
-    ) -> Result<usize, Errno> {
+    pub fn right_pad<W: Write + fmt::Write>(&self, output: &mut W, len: usize) -> EResult<usize> {
         if self.left_adjust {
             self.pad(output, len)
         } else {
-            Ok(0)
+            EResult::Ok(0)
         }
     }
 
@@ -181,7 +173,7 @@ impl FmtOpts {
         spec: FmtSpec,
         output: &mut W,
         ap: &mut VaList,
-    ) -> Result<usize, Errno> {
+    ) -> EResult<usize> {
         let mut buffer = [0; 64];
 
         let len = match spec {
@@ -214,7 +206,7 @@ impl FmtOpts {
                     let lpad = self.left_pad(output, bytes.len())?;
                     let len = output.write(bytes)?;
                     let rpad = self.right_pad(output, bytes.len())?;
-                    return Ok(lpad + len + rpad);
+                    return EResult::Ok(lpad + len + rpad);
                 }
             }
             FmtSpec::String if self.size == FmtSize::Long => {
@@ -242,7 +234,7 @@ impl FmtOpts {
                     let lpad = self.left_pad(output, bytes.len())?;
                     let len = output.write(bytes)?;
                     let rpad = self.right_pad(output, bytes.len())?;
-                    return Ok(lpad + len + rpad);
+                    return EResult::Ok(lpad + len + rpad);
                 }
             }
             FmtSpec::Char if self.size == FmtSize::Normal => {
@@ -278,7 +270,7 @@ impl FmtOpts {
         let count = output.write(&buffer[..len])?;
         let rpad = self.right_pad(output, len)?;
 
-        Ok(lpad + count + rpad)
+        EResult::Ok(lpad + count + rpad)
     }
 }
 
diff --git a/src/header/stdio/printf/mod.rs b/src/header/stdio/printf/mod.rs
index 3c5b12c..88a6cfa 100644
--- a/src/header/stdio/printf/mod.rs
+++ b/src/header/stdio/printf/mod.rs
@@ -3,9 +3,11 @@ use core::{
     fmt,
 };
 
-use yggdrasil_rt::{io::RawFd, sys as syscall};
-
-use crate::{error::EResult, header::errno::Errno, io::Write};
+use crate::{
+    error::{CIntCountResult, EResult, TryFromExt},
+    file::RawFile,
+    io::Write,
+};
 
 use self::format::{FmtOpts, FmtRadix, FmtSign, FmtSize, FmtSpec};
 
@@ -21,7 +23,7 @@ struct StringWriter {
 }
 
 struct FdWriter {
-    fd: RawFd,
+    file: RawFile,
 }
 
 impl StringWriter {
@@ -35,7 +37,7 @@ impl StringWriter {
 }
 
 impl Write for StringWriter {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno> {
+    fn write(&mut self, data: &[u8]) -> EResult<usize> {
         let count = core::cmp::min(self.capacity - self.position, data.len());
         if count > 0 {
             let dst = unsafe {
@@ -44,41 +46,40 @@ impl Write for StringWriter {
             dst.copy_from_slice(&data[..count]);
             self.position += count;
         }
-        Ok(count)
+        EResult::Ok(count)
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
+    fn flush(&mut self) -> EResult<()> {
         todo!()
     }
 }
 
 impl fmt::Write for StringWriter {
     fn write_str(&mut self, s: &str) -> fmt::Result {
-        self.write(s.as_bytes()).map_err(|_| fmt::Error)?;
+        self.write(s.as_bytes()).into_result(|_| fmt::Error, true)?;
         Ok(())
     }
 }
 
 impl FdWriter {
-    pub fn new(fd: RawFd) -> Self {
-        Self { fd }
+    pub fn new(file: RawFile) -> Self {
+        Self { file }
     }
 }
 
 impl Write for FdWriter {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno> {
-        let count = EResult::from(unsafe { syscall::write(self.fd, data) })?;
-        Ok(count)
+    fn write(&mut self, data: &[u8]) -> EResult<usize> {
+        self.file.write(data)
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
-        todo!()
+    fn flush(&mut self) -> EResult<()> {
+        self.file.flush()
     }
 }
 
 impl fmt::Write for FdWriter {
     fn write_str(&mut self, s: &str) -> fmt::Result {
-        self.write(s.as_bytes()).map_err(|_| fmt::Error)?;
+        self.write(s.as_bytes()).into_result(|_| fmt::Error, true)?;
         Ok(())
     }
 }
@@ -87,7 +88,7 @@ fn printf_inner<W: Write + fmt::Write>(
     output: &mut W,
     format: &[u8],
     mut ap: VaList,
-) -> Result<usize, Errno> {
+) -> EResult<usize> {
     let mut fmt = format.into_iter();
     let mut count = 0;
 
@@ -181,41 +182,51 @@ fn printf_inner<W: Write + fmt::Write>(
         }
     }
 
-    Ok(count)
+    EResult::Ok(count)
 }
 
 #[no_mangle]
-unsafe extern "C" fn printf(format: *const c_char, mut args: ...) -> c_int {
+unsafe extern "C" fn printf(format: *const c_char, mut args: ...) -> CIntCountResult {
     vfprintf(stdout, format, args.as_va_list())
 }
 
 #[no_mangle]
-unsafe extern "C" fn fprintf(stream: *mut FILE, format: *const c_char, mut args: ...) -> c_int {
+unsafe extern "C" fn fprintf(
+    stream: *mut FILE,
+    format: *const c_char,
+    mut args: ...
+) -> CIntCountResult {
     vfprintf(stream, format, args.as_va_list())
 }
 
 #[no_mangle]
-unsafe extern "C" fn vprintf(format: *const c_char, ap: VaList) -> c_int {
+unsafe extern "C" fn vprintf(format: *const c_char, ap: VaList) -> CIntCountResult {
     vfprintf(stdout, format, ap)
 }
 
 #[no_mangle]
-unsafe extern "C" fn vfprintf(stream: *mut FILE, format: *const c_char, ap: VaList) -> c_int {
+unsafe extern "C" fn vfprintf(
+    stream: *mut FILE,
+    format: *const c_char,
+    ap: VaList,
+) -> CIntCountResult {
     if format.is_null() {
         panic!();
     }
     let stream = stream.as_mut().unwrap();
     let format = CStr::from_ptr(format);
 
-    match printf_inner(stream, format.to_bytes(), ap) {
-        // TODO handle this
-        Ok(count) => count as c_int,
-        Err(_) => -1,
-    }
+    let count = printf_inner(stream, format.to_bytes(), ap)?;
+
+    CIntCountResult(count.try_into().unwrap())
 }
 
 #[no_mangle]
-unsafe extern "C" fn sprintf(str: *mut c_char, format: *const c_char, mut args: ...) -> c_int {
+unsafe extern "C" fn sprintf(
+    str: *mut c_char,
+    format: *const c_char,
+    mut args: ...
+) -> CIntCountResult {
     vsnprintf(str, usize::MAX, format, args.as_va_list())
 }
 
@@ -225,12 +236,16 @@ unsafe extern "C" fn snprintf(
     len: usize,
     format: *const c_char,
     mut args: ...
-) -> c_int {
+) -> CIntCountResult {
     vsnprintf(str, len, format, args.as_va_list())
 }
 
 #[no_mangle]
-unsafe extern "C" fn vsprintf(str: *mut c_char, format: *const c_char, ap: VaList) -> c_int {
+unsafe extern "C" fn vsprintf(
+    str: *mut c_char,
+    format: *const c_char,
+    ap: VaList,
+) -> CIntCountResult {
     vsnprintf(str, usize::MAX, format, ap)
 }
 
@@ -240,12 +255,12 @@ unsafe extern "C" fn vsnprintf(
     len: usize,
     format: *const c_char,
     ap: VaList,
-) -> c_int {
+) -> CIntCountResult {
     if format.is_null() {
         panic!();
     }
     if len == 0 {
-        return 0;
+        return CIntCountResult(0);
     }
     if str.is_null() {
         // TODO output the length
@@ -254,33 +269,26 @@ unsafe extern "C" fn vsnprintf(
     let mut writer = StringWriter::new(str, len);
     let format = CStr::from_ptr(format);
 
-    match printf_inner(&mut writer, format.to_bytes(), ap) {
-        // TODO handle this
-        Ok(count) => count as c_int,
-        Err(_) => -1,
-    }
+    let count = printf_inner(&mut writer, format.to_bytes(), ap)?;
+
+    CIntCountResult(count.try_into().unwrap())
 }
 
 #[no_mangle]
-unsafe extern "C" fn dprintf(fd: c_int, format: *const c_char, mut args: ...) -> c_int {
+unsafe extern "C" fn dprintf(fd: c_int, format: *const c_char, mut args: ...) -> CIntCountResult {
     vdprintf(fd, format, args.as_va_list())
 }
 
 #[no_mangle]
-unsafe extern "C" fn vdprintf(fd: c_int, format: *const c_char, ap: VaList) -> c_int {
+unsafe extern "C" fn vdprintf(fd: c_int, format: *const c_char, ap: VaList) -> CIntCountResult {
     if format.is_null() {
         panic!();
     }
-    if fd < 0 {
-        // TODO set errno and return
-        todo!();
-    }
-    let mut writer = FdWriter::new(RawFd(fd as u32));
+    let file = RawFile::e_try_from(fd)?;
+    let mut writer = FdWriter::new(file);
     let format = CStr::from_ptr(format);
 
-    match printf_inner(&mut writer, format.to_bytes(), ap) {
-        // TODO handle this
-        Ok(count) => count as c_int,
-        Err(_) => -1,
-    }
+    let count = printf_inner(&mut writer, format.to_bytes(), ap)?;
+
+    CIntCountResult(count.try_into().unwrap())
 }
diff --git a/src/header/stdio/scanf/char_set.rs b/src/header/stdio/scanf/char_set.rs
index faaba09..9331a64 100644
--- a/src/header/stdio/scanf/char_set.rs
+++ b/src/header/stdio/scanf/char_set.rs
@@ -1,6 +1,6 @@
 use core::ops::RangeInclusive;
 
-use super::ScanError;
+use super::FormatError;
 
 pub struct ScanCharSet {
     mask: [u64; 4],
@@ -17,7 +17,7 @@ impl ScanCharSet {
 
     pub fn from_format_iter<'a, I: Iterator<Item = &'a u8>>(
         mut it: I,
-    ) -> Result<(I, Self), ScanError> {
+    ) -> Result<(I, Self), FormatError> {
         let mut maybe_close_bracket = true;
         let mut hyphen = false;
         let mut start: Option<u8> = None;
@@ -51,7 +51,7 @@ impl ScanCharSet {
             if ch == b'-' {
                 if hyphen {
                     // "--"?
-                    return Err(ScanError::InvalidFormat);
+                    return Err(FormatError);
                 }
 
                 hyphen = true;
@@ -62,7 +62,7 @@ impl ScanCharSet {
             if hyphen {
                 let Some(start) = start.take() else {
                     // "-x" without start?
-                    return Err(ScanError::InvalidFormat);
+                    return Err(FormatError);
                 };
 
                 let same_category = (start.is_ascii_digit() && ch.is_ascii_digit())
@@ -73,7 +73,7 @@ impl ScanCharSet {
                     hyphen = false;
                     set.insert_range(start..=ch);
                 } else {
-                    return Err(ScanError::InvalidFormat);
+                    return Err(FormatError);
                 }
             } else {
                 if let Some(start) = start.replace(ch) {
diff --git a/src/header/stdio/scanf/mod.rs b/src/header/stdio/scanf/mod.rs
index 8b551dd..69c07f4 100644
--- a/src/header/stdio/scanf/mod.rs
+++ b/src/header/stdio/scanf/mod.rs
@@ -1,6 +1,9 @@
-use core::ffi::{c_char, c_int, CStr, VaList};
+use core::ffi::{c_char, CStr, VaList};
 
-use crate::header::errno::Errno;
+use crate::{
+    error::{CEofResult, EResult},
+    header::errno::{Errno, ESUCCESS},
+};
 
 use self::{
     char_set::ScanCharSet,
@@ -14,25 +17,16 @@ mod char_set;
 mod format;
 mod reader;
 
-pub enum ScanError {
-    ReadError(Errno),
-    InvalidFormat,
-}
-
 pub enum ConversionError {
-    ReadError(Errno),
+    Error(Errno),
     ConversionFailed,
 }
 
-impl From<Errno> for ScanError {
-    fn from(value: Errno) -> Self {
-        Self::ReadError(value)
-    }
-}
+pub struct FormatError;
 
 impl From<Errno> for ConversionError {
     fn from(value: Errno) -> Self {
-        Self::ReadError(value)
+        Self::Error(value)
     }
 }
 
@@ -40,7 +34,7 @@ fn scanf_inner<G: GetChar>(
     stream: &mut ScanReader<G>,
     format: &[u8],
     mut ap: VaList,
-) -> Result<usize, ScanError> {
+) -> EResult<usize> {
     let mut it = format.into_iter();
     let mut matched = 0;
     let mut skip_space = false;
@@ -128,7 +122,10 @@ fn scanf_inner<G: GetChar>(
                 b'o' => ScanSpec::Unsigned(ScanRadix::Oct),
                 b's' => ScanSpec::Word,
                 b'[' => {
-                    let (new_it, set) = ScanCharSet::from_format_iter(it)?;
+                    let (new_it, set) = match ScanCharSet::from_format_iter(it) {
+                        Ok(v) => v,
+                        Err(FormatError) => return EResult::Err(ESUCCESS),
+                    };
                     it = new_it;
                     ScanSpec::Chars(set)
                 }
@@ -138,42 +135,46 @@ fn scanf_inner<G: GetChar>(
                 b'%' => ScanSpec::Percent,
                 b'f' | b'e' | b'g' | b'E' | b'a' => todo!(),
                 // Unrecognized specifier
-                _ => return Err(ScanError::InvalidFormat),
+                _ => return EResult::Err(ESUCCESS),
             }
         } else {
             // No specifier after %
-            return Err(ScanError::InvalidFormat);
+            return EResult::Err(ESUCCESS);
         };
 
         matched += match opts.scan(stream, spec, &mut ap) {
             Ok(matched) => matched,
             Err(ConversionError::ConversionFailed) => break,
-            Err(ConversionError::ReadError(err)) => return Err(ScanError::ReadError(err)),
+            Err(ConversionError::Error(err)) => return EResult::Err(err),
         };
     }
 
     // TODO report end of stream before anything is matched
 
-    Ok(matched)
+    EResult::Ok(matched)
 }
 
 #[no_mangle]
-unsafe extern "C" fn fscanf(stream: *mut FILE, format: *const c_char, mut args: ...) -> c_int {
+unsafe extern "C" fn fscanf(stream: *mut FILE, format: *const c_char, mut args: ...) -> CEofResult {
     vfscanf(stream, format, args.as_va_list())
 }
 
 #[no_mangle]
-unsafe extern "C" fn scanf(format: *const c_char, mut args: ...) -> c_int {
+unsafe extern "C" fn scanf(format: *const c_char, mut args: ...) -> CEofResult {
     vfscanf(stdin, format, args.as_va_list())
 }
 
 #[no_mangle]
-unsafe extern "C" fn sscanf(str: *const c_char, format: *const c_char, mut args: ...) -> c_int {
+unsafe extern "C" fn sscanf(
+    str: *const c_char,
+    format: *const c_char,
+    mut args: ...
+) -> CEofResult {
     vsscanf(str, format, args.as_va_list())
 }
 
 #[no_mangle]
-unsafe extern "C" fn vfscanf(stream: *mut FILE, format: *const c_char, ap: VaList) -> c_int {
+unsafe extern "C" fn vfscanf(stream: *mut FILE, format: *const c_char, ap: VaList) -> CEofResult {
     if format.is_null() {
         panic!();
     }
@@ -183,19 +184,18 @@ unsafe extern "C" fn vfscanf(stream: *mut FILE, format: *const c_char, ap: VaLis
 
     let mut reader = ScanReader::new(stream);
 
-    match scanf_inner(&mut reader, format.to_bytes(), ap) {
-        Ok(count) => count.try_into().unwrap(),
-        Err(_) => -1,
-    }
+    let count = scanf_inner(&mut reader, format.to_bytes(), ap)?;
+
+    CEofResult(count.try_into().unwrap())
 }
 
 #[no_mangle]
-unsafe extern "C" fn vscanf(format: *const c_char, ap: VaList) -> c_int {
+unsafe extern "C" fn vscanf(format: *const c_char, ap: VaList) -> CEofResult {
     vfscanf(stdin, format, ap)
 }
 
 #[no_mangle]
-unsafe extern "C" fn vsscanf(str: *const c_char, format: *const c_char, ap: VaList) -> c_int {
+unsafe extern "C" fn vsscanf(str: *const c_char, format: *const c_char, ap: VaList) -> CEofResult {
     if str.is_null() || format.is_null() {
         panic!();
     }
@@ -206,8 +206,7 @@ unsafe extern "C" fn vsscanf(str: *const c_char, format: *const c_char, ap: VaLi
     let mut str_it = str.to_bytes().into_iter();
     let mut reader = ScanReader::new(&mut str_it);
 
-    match scanf_inner(&mut reader, format.to_bytes(), ap) {
-        Ok(count) => count.try_into().unwrap(),
-        Err(_) => -1,
-    }
+    let count = scanf_inner(&mut reader, format.to_bytes(), ap)?;
+
+    CEofResult(count.try_into().unwrap())
 }
diff --git a/src/header/stdio/scanf/reader.rs b/src/header/stdio/scanf/reader.rs
index 75611bf..2632c51 100644
--- a/src/header/stdio/scanf/reader.rs
+++ b/src/header/stdio/scanf/reader.rs
@@ -1,10 +1,7 @@
-use crate::{
-    header::{errno::Errno, stdio::FILE},
-    io::Read,
-};
+use crate::{error::EResult, header::stdio::FILE, io::Read};
 
 pub trait GetChar {
-    fn getc(&mut self) -> Result<Option<u8>, Errno>;
+    fn getc(&mut self) -> EResult<Option<u8>>;
 }
 
 pub struct ScanReader<'a, G: GetChar> {
@@ -14,19 +11,19 @@ pub struct ScanReader<'a, G: GetChar> {
 }
 
 impl GetChar for FILE {
-    fn getc(&mut self) -> Result<Option<u8>, Errno> {
+    fn getc(&mut self) -> EResult<Option<u8>> {
         let mut buf = [0];
         match self.read(&mut buf) {
-            Ok(1) => Ok(Some(buf[0])),
-            Ok(_) => Ok(None),
-            Err(err) => Err(err),
+            EResult::Ok(1) => EResult::Ok(Some(buf[0])),
+            EResult::Ok(_) => EResult::Ok(None),
+            EResult::Err(err) => EResult::Err(err),
         }
     }
 }
 
 impl<'a, I: Iterator<Item = &'a u8>> GetChar for I {
-    fn getc(&mut self) -> Result<Option<u8>, Errno> {
-        Ok(self.next().copied())
+    fn getc(&mut self) -> EResult<Option<u8>> {
+        EResult::Ok(self.next().copied())
     }
 }
 
@@ -39,11 +36,11 @@ impl<'a, G: GetChar> ScanReader<'a, G> {
         }
     }
 
-    fn getc(&mut self) -> Result<Option<u8>, Errno> {
+    fn getc(&mut self) -> EResult<Option<u8>> {
         match self.getter.getc() {
-            Ok(Some(n)) => {
+            EResult::Ok(Some(n)) => {
                 self.consumed_count += 1;
-                Ok(Some(n))
+                EResult::Ok(Some(n))
             }
             e => e,
         }
@@ -53,16 +50,16 @@ impl<'a, G: GetChar> ScanReader<'a, G> {
         self.consumed_count
     }
 
-    pub fn peek(&mut self) -> Result<Option<u8>, Errno> {
+    pub fn peek(&mut self) -> EResult<Option<u8>> {
         if self.buffer.is_none() {
             self.buffer = self.getc()?;
         }
-        Ok(self.buffer)
+        EResult::Ok(self.buffer)
     }
 
-    pub fn next(&mut self) -> Result<Option<u8>, Errno> {
+    pub fn next(&mut self) -> EResult<Option<u8>> {
         match self.buffer.take() {
-            Some(v) => Ok(Some(v)),
+            Some(v) => EResult::Ok(Some(v)),
             None => self.getc(),
         }
     }
diff --git a/src/header/stdio/unlocked.rs b/src/header/stdio/unlocked.rs
index 4af0bbf..2fe8265 100644
--- a/src/header/stdio/unlocked.rs
+++ b/src/header/stdio/unlocked.rs
@@ -1,13 +1,11 @@
 use core::ffi::{c_char, c_int, c_void, CStr};
 
-use yggdrasil_rt::io::RawFd;
-
 use crate::{
-    error::{self, CSizeResult, CZeroResult},
+    error::{CEofResult, CFdResult, CIntZeroResult, CUsizeResult, OptionExt},
     header::errno::EBADF,
 };
 
-use super::{stdin, stdout, FileFlags, EOF, FILE};
+use super::{stdin, stdout, FileFlags, FILE};
 
 #[no_mangle]
 pub unsafe extern "C" fn flockfile(stream: *mut FILE) {
@@ -16,12 +14,10 @@ pub unsafe extern "C" fn flockfile(stream: *mut FILE) {
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn ftrylockfile(stream: *mut FILE) -> c_int {
+pub unsafe extern "C" fn ftrylockfile(stream: *mut FILE) -> CIntZeroResult {
     let stream = stream.as_mut().unwrap();
-    match stream.try_lock() {
-        true => 0,
-        false => -1,
-    }
+    stream.try_lock()?;
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -49,15 +45,10 @@ pub unsafe extern "C" fn clearerr_unlocked(stream: *mut FILE) {
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fileno_unlocked(stream: *mut FILE) -> c_int {
+pub unsafe extern "C" fn fileno_unlocked(stream: *mut FILE) -> CFdResult {
     let stream = stream.as_mut().unwrap();
-    match stream.as_raw_fd_opt_unlocked() {
-        Some(RawFd(fd)) => fd as _,
-        None => {
-            error::set_errno(EBADF);
-            -1
-        }
-    }
+    let fd = stream.as_raw_fd_opt_unlocked().e_ok_or(EBADF)?;
+    CFdResult::success(fd)
 }
 
 #[no_mangle]
@@ -66,14 +57,16 @@ pub unsafe extern "C" fn fwrite_unlocked(
     size: usize,
     nmemb: usize,
     stream: *mut FILE,
-) -> usize {
+) -> CUsizeResult {
     if ptr.is_null() {
         panic!();
     }
     let stream = stream.as_mut().unwrap();
     let data = core::slice::from_raw_parts(ptr as *const u8, size * nmemb);
 
-    stream.write_unlocked(data).into_size_status() / size
+    let count = stream.write_unlocked(data)?;
+
+    CUsizeResult(count / size)
 }
 
 #[no_mangle]
@@ -82,62 +75,64 @@ pub unsafe extern "C" fn fread_unlocked(
     size: usize,
     nmemb: usize,
     stream: *mut FILE,
-) -> usize {
+) -> CUsizeResult {
     if ptr.is_null() {
         panic!();
     }
     let stream = stream.as_mut().unwrap();
     let data = core::slice::from_raw_parts_mut(ptr as *mut u8, size * nmemb);
 
-    stream.read_unlocked(data).into_size_status() / size
+    let count = stream.read_unlocked(data)?;
+
+    CUsizeResult(count / size)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fflush_unlocked(stream: *mut FILE) -> c_int {
+pub unsafe extern "C" fn fflush_unlocked(stream: *mut FILE) -> CEofResult {
     if let Some(stream) = stream.as_mut() {
-        stream.flush_unlocked().into_eof_status()
+        stream.flush_unlocked()?;
     } else {
-        super::fflush_all_unlocked().into_eof_status()
+        super::fflush_all_unlocked()?;
     }
+
+    CEofResult(0)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fgetc_unlocked(stream: *mut FILE) -> c_int {
+pub unsafe extern "C" fn fgetc_unlocked(stream: *mut FILE) -> CEofResult {
     let stream = stream.as_mut().unwrap();
     let mut buf = [0];
-    match stream.read_unlocked(&mut buf) {
-        Ok(1) => buf[0] as c_int,
-        Ok(_) => EOF,
-        Err(_) => EOF,
+    match stream.read_unlocked(&mut buf)? {
+        1 => CEofResult(buf[0] as _),
+        _ => CEofResult::ERR,
     }
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn getc_unlocked(stream: *mut FILE) -> c_int {
+pub unsafe extern "C" fn getc_unlocked(stream: *mut FILE) -> CEofResult {
     fgetc_unlocked(stream)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn getchar_unlocked() -> c_int {
+pub unsafe extern "C" fn getchar_unlocked() -> CEofResult {
     fgetc_unlocked(stdin)
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn putchar_unlocked(c: c_int) -> c_int {
+pub unsafe extern "C" fn putchar_unlocked(c: c_int) -> CEofResult {
     fputc_unlocked(c, stdout)
 }
 
 #[no_mangle]
-pub unsafe fn fputc_unlocked(c: c_int, stream: *mut FILE) -> c_int {
+pub unsafe fn fputc_unlocked(c: c_int, stream: *mut FILE) -> CEofResult {
     let stream = stream.as_mut().unwrap();
 
-    match stream.write_unlocked(&[c as u8]) {
-        Ok(_) => c,
-        Err(_) => EOF,
-    }
+    stream.write_unlocked(&[c as u8])?;
+
+    CEofResult(0)
 }
 
-pub unsafe fn fputs_unlocked(s: *const c_char, stream: *mut FILE) -> c_int {
+pub unsafe fn fputs_unlocked(s: *const c_char, stream: *mut FILE) -> CEofResult {
     if s.is_null() {
         panic!();
     }
@@ -145,8 +140,8 @@ pub unsafe fn fputs_unlocked(s: *const c_char, stream: *mut FILE) -> c_int {
     let s = CStr::from_ptr(s);
     let stream = stream.as_mut().unwrap();
 
-    match stream.write_unlocked(s.to_bytes()) {
-        Ok(_) => 0,
-        Err(_) => EOF,
-    }
+    // TODO write_all_unlocked
+    stream.write_unlocked(s.to_bytes())?;
+
+    CEofResult(0)
 }
diff --git a/src/header/stdlib/malloc.rs b/src/header/stdlib/malloc.rs
index 3925a61..e1d8eb2 100644
--- a/src/header/stdlib/malloc.rs
+++ b/src/header/stdlib/malloc.rs
@@ -1,98 +1,28 @@
-use core::{
-    alloc::{GlobalAlloc, Layout},
-    ffi::c_void,
-    intrinsics,
-    ptr::null_mut,
-};
+use core::{ffi::c_void, ptr::NonNull};
 
-use crate::{allocator::GLOBAL_ALLOCATOR, error, header::errno::ENOMEM};
+use crate::{allocator, error::CPtrResult};
 
-unsafe fn alloc_inner(size: usize) -> *mut c_void {
-    let size = (size + 15) & !15;
-    let layout = Layout::from_size_align(size + 16, 16).unwrap();
-    let ptr = GLOBAL_ALLOCATOR.alloc(layout);
-
-    if ptr.is_null() {
-        error::set_errno(ENOMEM);
-        return ptr as *mut c_void;
-    }
-
-    *(ptr as *mut u64) = (size + 16) as u64;
-    *(ptr as *mut u64).add(1) = 16 as u64;
-
-    ptr.add(16) as *mut c_void
-}
-
-unsafe fn get_allocation(ptr: *mut c_void) -> (*mut u8, Layout) {
-    assert!(ptr as usize > 0x10);
-    let base = (ptr as *mut u8).sub(16);
-    let size = *(base as *mut u64);
-    let align = *(base as *mut u64).add(1);
-    let layout = Layout::from_size_align(size as _, align as _).unwrap();
-    (base, layout)
+#[no_mangle]
+pub unsafe extern "C" fn calloc(nmemb: usize, size: usize) -> CPtrResult<c_void> {
+    let ptr = allocator::c_allocate_zeroed(nmemb, size)?;
+    CPtrResult::success(ptr.cast())
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn calloc(nmemb: usize, size: usize) -> *mut c_void {
-    match nmemb.checked_mul(size) {
-        Some(size) => {
-            let ptr = malloc(size);
-            if !ptr.is_null() {
-                intrinsics::write_bytes(ptr as *mut u8, 0, size);
-            }
-            ptr
-        }
-        None => {
-            error::set_errno(ENOMEM);
-            null_mut()
-        }
-    }
+unsafe extern "C" fn malloc(size: usize) -> CPtrResult<c_void> {
+    let ptr = allocator::c_allocate(size)?;
+    CPtrResult::success(ptr.cast())
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn malloc(size: usize) -> *mut c_void {
-    alloc_inner(size)
+unsafe extern "C" fn realloc(ptr: *mut c_void, new_size: usize) -> CPtrResult<c_void> {
+    let ptr = allocator::c_reallocate(NonNull::new(ptr).map(NonNull::cast), new_size)?;
+    CPtrResult::success(ptr.cast())
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn realloc(ptr: *mut c_void, new_size: usize) -> *mut c_void {
-    if ptr.is_null() {
-        return malloc(new_size);
+unsafe extern "C" fn free(ptr: *mut c_void) {
+    if let Some(ptr) = NonNull::new(ptr) {
+        allocator::c_free(ptr.cast())
     }
-    if new_size == 0 {
-        free(ptr);
-        return null_mut();
-    }
-
-    // TODO: implement realloc in libyalloc?
-    let (_, old_layout) = get_allocation(ptr);
-    let new_ptr = malloc(new_size);
-
-    if !new_ptr.is_null() {
-        yggdrasil_rt::memcpy(new_ptr as _, ptr as _, old_layout.size());
-        free(ptr);
-    }
-
-    new_ptr
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn free(ptr: *mut c_void) {
-    if ptr.is_null() {
-        return;
-    }
-    let (allocation, layout) = get_allocation(ptr);
-    GLOBAL_ALLOCATOR.dealloc(allocation, layout);
-}
-
-#[no_mangle]
-unsafe extern "C" fn ymalloc(size: usize) -> *mut c_void {
-    let ptr = GLOBAL_ALLOCATOR.alloc(Layout::from_size_align(size, 8).unwrap());
-    ptr as _
-}
-
-#[no_mangle]
-unsafe extern "C" fn yfree(ptr: *mut c_void, size: usize) {
-    assert!(!ptr.is_null());
-    GLOBAL_ALLOCATOR.dealloc(ptr as _, Layout::from_size_align(size, 8).unwrap());
 }
diff --git a/src/header/stdlib/mod.rs b/src/header/stdlib/mod.rs
index 7b16327..d28bd18 100644
--- a/src/header/stdlib/mod.rs
+++ b/src/header/stdlib/mod.rs
@@ -27,8 +27,6 @@ size_t        wcstombs(char *restrict, const wchar_t *restrict, size_t);
 int           wctomb(char *, wchar_t);
 */
 
-pub use malloc::{calloc, free, malloc, realloc};
-
 pub const EXIT_SUCCESS: c_int = 0;
 pub const EXIT_FAILURE: c_int = 1;
 
diff --git a/src/header/stdlib/process.rs b/src/header/stdlib/process.rs
index 38e6313..6e440d0 100644
--- a/src/header/stdlib/process.rs
+++ b/src/header/stdlib/process.rs
@@ -1,16 +1,17 @@
 use core::{
     ffi::{c_char, c_int, CStr},
-    ptr::null_mut,
+    ptr::NonNull,
 };
 
-use crate::process;
+use crate::{
+    error::{CIntZeroResult, CPtrResult},
+    process,
+};
 
 #[no_mangle]
-pub unsafe extern "C" fn atexit(f: extern "C" fn()) -> c_int {
-    match process::register_atexit(f) {
-        Ok(()) => 0,
-        Err(_) => -1,
-    }
+pub unsafe extern "C" fn atexit(f: extern "C" fn()) -> CIntZeroResult {
+    process::register_atexit(f)?;
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -29,15 +30,13 @@ pub unsafe extern "C" fn abort() -> ! {
 }
 
 #[no_mangle]
-unsafe extern "C" fn getenv(name: *const c_char) -> *mut c_char {
+unsafe extern "C" fn getenv(name: *const c_char) -> CPtrResult<c_char> {
     if name.is_null() {
         panic!();
     }
     let name = CStr::from_ptr(name);
-    match process::getenv_raw(name.to_bytes()) {
-        Some(data) => data.as_ptr() as _,
-        None => null_mut(),
-    }
+    let entry = process::getenv_raw(name.to_bytes())?;
+    CPtrResult::success(NonNull::new_unchecked(entry.as_ptr() as _))
 }
 
 #[no_mangle]
@@ -46,30 +45,32 @@ unsafe extern "C" fn putenv(string: *mut c_char) -> c_int {
 }
 
 #[no_mangle]
-unsafe extern "C" fn setenv(name: *const c_char, value: *const c_char, overwrite: c_int) -> c_int {
+unsafe extern "C" fn setenv(
+    name: *const c_char,
+    value: *const c_char,
+    overwrite: c_int,
+) -> CIntZeroResult {
     if name.is_null() || value.is_null() {
         panic!();
     }
     let name = CStr::from_ptr(name);
     let value = CStr::from_ptr(value);
 
-    match process::setenv_raw(name.to_bytes(), Some(value.to_bytes()), overwrite != 0) {
-        Ok(_) => 0,
-        Err(_) => -1,
-    }
+    process::setenv_raw(name.to_bytes(), Some(value.to_bytes()), overwrite != 0)?;
+
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
-unsafe extern "C" fn unsetenv(name: *const c_char) -> c_int {
+unsafe extern "C" fn unsetenv(name: *const c_char) -> CIntZeroResult {
     if name.is_null() {
         panic!();
     }
     let name = CStr::from_ptr(name);
 
-    match process::setenv_raw(name.to_bytes(), None, true) {
-        Ok(_) => 0,
-        Err(_) => -1,
-    }
+    process::setenv_raw(name.to_bytes(), None, true)?;
+
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
diff --git a/src/header/string/str.rs b/src/header/string/str.rs
index a19680b..06425b1 100644
--- a/src/header/string/str.rs
+++ b/src/header/string/str.rs
@@ -7,10 +7,11 @@ use core::{
 use yggdrasil_rt::memcpy;
 
 use crate::{
+    allocator,
+    error::CPtrResult,
     header::{
         errno::{self, Errno},
         locale::locale_t,
-        stdlib::malloc,
         string::strlen,
     },
     util::Nullable,
@@ -95,12 +96,12 @@ unsafe extern "C" fn strcspn(mut s: *const c_char, reject: *const c_char) -> usi
 }
 
 #[no_mangle]
-unsafe extern "C" fn strdup(s: *const c_char) -> *mut c_char {
+unsafe extern "C" fn strdup(s: *const c_char) -> CPtrResult<c_char> {
     s.ensure();
     let len = strlen(s);
-    let data = malloc(len + 1);
-    memcpy(data as _, s as _, len + 1);
-    data as _
+    let data = allocator::c_allocate(len + 1)?;
+    memcpy(data.cast().as_ptr(), s as _, len + 1);
+    CPtrResult::success(data.cast())
 }
 
 unsafe fn strerror_inner(e: c_int) -> *const c_char {
diff --git a/src/header/sys_stat/mod.rs b/src/header/sys_stat/mod.rs
index 3ee3221..2fc92f2 100644
--- a/src/header/sys_stat/mod.rs
+++ b/src/header/sys_stat/mod.rs
@@ -3,13 +3,12 @@ use core::ffi::{c_char, c_int, CStr};
 use yggdrasil_rt::io::{FileAttr, FileMode, FileType, RawFd};
 
 use crate::{
-    error::{self, CZeroResult},
+    error::{CIntZeroResult, TryFromExt},
     io,
-    util::Nullable,
+    util::{self, Nullable},
 };
 
 use super::{
-    errno::EBADF,
     fcntl::{AT_FDCWD, AT_SYMLINK_NOFOLLOW},
     sys_time::__ygg_timespec_t,
     sys_types::{blkcnt_t, blksize_t, dev_t, gid_t, ino_t, mode_t, nlink_t, off_t, uid_t},
@@ -115,29 +114,20 @@ unsafe extern "C" fn umask(mode: mode_t) -> mode_t {
 // Create stuff
 
 #[no_mangle]
-unsafe extern "C" fn mkdir(pathname: *const c_char, mode: mode_t) -> c_int {
+unsafe extern "C" fn mkdir(pathname: *const c_char, mode: mode_t) -> CIntZeroResult {
     mkdirat(AT_FDCWD, pathname, mode)
 }
 
 #[no_mangle]
-unsafe extern "C" fn mkdirat(atfd: c_int, pathname: *const c_char, mode: mode_t) -> c_int {
+unsafe extern "C" fn mkdirat(atfd: c_int, pathname: *const c_char, mode: mode_t) -> CIntZeroResult {
     pathname.ensure();
     let pathname = CStr::from_ptr(pathname).to_str().unwrap();
-
-    // TODO move this to a function
-    let atfd = match atfd {
-        // Same as stat()
-        AT_FDCWD => None,
-        0.. => Some(RawFd(atfd as _)),
-        _ => {
-            error::set_errno(EBADF);
-            return -1;
-        }
-    };
-
+    let atfd = util::at_fd(atfd)?;
     let mode = FileMode::new((mode & 0o777) as u32);
 
-    io::create_directory(atfd, pathname, mode).into_zero_status()
+    io::create_directory(atfd, pathname, mode)?;
+
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -168,22 +158,15 @@ unsafe extern "C" fn mknodat(
 // File status
 
 #[no_mangle]
-unsafe extern "C" fn fstat(fd: c_int, statbuf: *mut stat) -> c_int {
-    if fd < 0 {
-        error::set_errno(EBADF);
-        return -1;
-    }
-
-    let attr = match io::get_metadata(Some(RawFd(fd as _)), "", false) {
-        Ok(attr) => attr,
-        Err(_) => return -1,
-    };
+unsafe extern "C" fn fstat(fd: c_int, statbuf: *mut stat) -> CIntZeroResult {
+    let fd = RawFd::e_try_from(fd)?;
+    let attr = io::get_metadata(Some(fd), "", false)?;
 
     if let Some(statbuf) = statbuf.as_mut() {
         *statbuf = attr.into();
     }
 
-    0
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -192,42 +175,28 @@ unsafe extern "C" fn fstatat(
     pathname: *const c_char,
     statbuf: *mut stat,
     opt: c_int,
-) -> c_int {
+) -> CIntZeroResult {
     pathname.ensure();
     let pathname = CStr::from_ptr(pathname).to_str().unwrap();
-
-    // TODO move this to a function
-    let atfd = match atfd {
-        // Same as stat()
-        AT_FDCWD => None,
-        0.. => Some(RawFd(atfd as _)),
-        _ => {
-            error::set_errno(EBADF);
-            return -1;
-        }
-    };
-
+    let atfd = util::at_fd(atfd)?;
     let follow = opt & AT_SYMLINK_NOFOLLOW == 0;
 
-    let attr = match io::get_metadata(atfd, pathname, follow) {
-        Ok(attr) => attr,
-        Err(_) => return -1,
-    };
+    let attr = io::get_metadata(atfd, pathname, follow)?;
 
     if let Some(statbuf) = statbuf.as_mut() {
         *statbuf = attr.into();
     }
 
-    0
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
-unsafe extern "C" fn lstat(pathname: *const c_char, statbuf: *mut stat) -> c_int {
+unsafe extern "C" fn lstat(pathname: *const c_char, statbuf: *mut stat) -> CIntZeroResult {
     fstatat(AT_FDCWD, pathname, statbuf, AT_SYMLINK_NOFOLLOW)
 }
 
 #[no_mangle]
-unsafe extern "C" fn stat(pathname: *const c_char, statbuf: *mut stat) -> c_int {
+unsafe extern "C" fn stat(pathname: *const c_char, statbuf: *mut stat) -> CIntZeroResult {
     fstatat(AT_FDCWD, pathname, statbuf, 0)
 }
 
diff --git a/src/header/sys_wait/mod.rs b/src/header/sys_wait/mod.rs
index d5e478f..48765cf 100644
--- a/src/header/sys_wait/mod.rs
+++ b/src/header/sys_wait/mod.rs
@@ -2,33 +2,31 @@ use core::ffi::c_int;
 
 use yggdrasil_rt::{process::ExitCode, sys as syscall};
 
-use super::{errno::Errno, sys_types::pid_t};
+use crate::error::{CPidResult, EResult};
 
-fn waitpid_inner(pid: u32) -> Result<ExitCode, Errno> {
+use super::sys_types::pid_t;
+
+fn waitpid_inner(pid: u32) -> EResult<ExitCode> {
     let mut exit_code = ExitCode::SUCCESS;
     unsafe { syscall::wait_process(pid, &mut exit_code) }?;
-    Ok(exit_code)
+    EResult::Ok(exit_code)
 }
 
 #[no_mangle]
-unsafe extern "C" fn waitpid(pid: pid_t, wstatus: *mut c_int, options: c_int) -> pid_t {
+unsafe extern "C" fn waitpid(pid: pid_t, wstatus: *mut c_int, options: c_int) -> CPidResult {
     let _ = options;
     if pid < 0 {
         todo!();
     }
-    let pid = pid as u32;
+    let pid: u32 = pid.try_into().unwrap();
+    let code = waitpid_inner(pid)?;
 
-    match waitpid_inner(pid) {
-        Ok(code) => {
-            if let Some(wstatus) = wstatus.as_mut() {
-                match code {
-                    ExitCode::Exited(code) => *wstatus = code,
-                    ExitCode::BySignal(_) => todo!(),
-                }
-            }
-
-            pid as pid_t
+    if let Some(wstatus) = wstatus.as_mut() {
+        match code {
+            ExitCode::Exited(code) => *wstatus = code,
+            ExitCode::BySignal(_signal) => todo!(),
         }
-        Err(_) => -1,
     }
+
+    CPidResult::success(pid)
 }
diff --git a/src/header/time/utility.rs b/src/header/time/utility.rs
index 44da52a..b6f23c0 100644
--- a/src/header/time/utility.rs
+++ b/src/header/time/utility.rs
@@ -1,9 +1,7 @@
-use core::{
-    ffi::{c_double, c_int},
-    time::Duration,
-};
+use core::{ffi::c_double, time::Duration};
 
 use crate::{
+    error::CIntZeroResult,
     header::{sys_time::__ygg_timespec_t, sys_types::time_t},
     util,
 };
@@ -12,27 +10,17 @@ use crate::{
 unsafe extern "C" fn nanosleep(
     rqtp: *const __ygg_timespec_t,
     rmtp: *mut __ygg_timespec_t,
-) -> c_int {
+) -> CIntZeroResult {
     let rqtp = rqtp.as_ref().unwrap();
+    if let Some(_rmtp) = rmtp.as_mut() {
+        todo!();
+    }
 
     let amount = Duration::from(*rqtp);
 
-    match util::nanosleep(amount, None) {
-        Ok(()) => {
-            if let Some(rmtp) = rmtp.as_mut() {
-                // Zero
-                *rmtp = __ygg_timespec_t::default();
-            }
+    util::nanosleep(amount, None)?;
 
-            0
-        }
-        Err(_) => {
-            if let Some(rmtp) = rmtp.as_mut() {
-                todo!();
-            }
-            -1
-        }
-    }
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
diff --git a/src/header/unistd/io.rs b/src/header/unistd/io.rs
index ef78c4e..ba1e187 100644
--- a/src/header/unistd/io.rs
+++ b/src/header/unistd/io.rs
@@ -3,7 +3,7 @@ use core::ffi::{c_char, c_int, c_long, c_void};
 use yggdrasil_rt::io::SeekFrom;
 
 use crate::{
-    error,
+    error::{CFdResult, CIntZeroResult, CIsizeResult, COffsetResult, EResult, TryFromExt},
     file::RawFile,
     header::{
         errno::EINVAL,
@@ -18,82 +18,69 @@ use crate::{
 pub const _PC_NAME_MAX: c_int = 1;
 pub const _PC_PATH_MAX: c_int = 2;
 
+fn seek_offset(whence: c_int, offset: off_t) -> EResult<SeekFrom> {
+    match whence {
+        SEEK_SET => EResult::Ok(SeekFrom::Start(offset.try_into().unwrap())),
+        SEEK_END => EResult::Ok(SeekFrom::End(offset.try_into().unwrap())),
+        SEEK_CUR => EResult::Ok(SeekFrom::Current(offset.try_into().unwrap())),
+        _ => EResult::Err(EINVAL),
+    }
+}
+
 #[no_mangle]
 unsafe extern "C" fn getcwd(buf: *mut c_char, size: usize) -> *mut c_char {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn close(fd: c_int) -> c_int {
-    let Ok(mut file) = RawFile::try_from(fd) else {
-        return -1;
-    };
-
-    match file.close() {
-        Ok(()) => 0,
-        Err(_) => -1,
-    }
+unsafe extern "C" fn close(fd: c_int) -> CIntZeroResult {
+    let mut file = RawFile::e_try_from(fd)?;
+    file.close()?;
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
-unsafe extern "C" fn unlink(pathname: *const c_char) -> c_int {
+unsafe extern "C" fn unlink(pathname: *const c_char) -> CIntZeroResult {
     unlinkat(AT_FDCWD, pathname, AT_SYMLINK_NOFOLLOW)
 }
 
 #[no_mangle]
-unsafe extern "C" fn unlinkat(atfd: c_int, pathname: *const c_char, flags: c_int) -> c_int {
+unsafe extern "C" fn unlinkat(
+    atfd: c_int,
+    pathname: *const c_char,
+    flags: c_int,
+) -> CIntZeroResult {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn write(fd: c_int, buf: *const c_void, count: usize) -> isize {
+unsafe extern "C" fn write(fd: c_int, buf: *const c_void, count: usize) -> CIsizeResult {
     buf.ensure();
 
-    let Ok(mut file) = RawFile::try_from(fd) else {
-        return -1;
-    };
+    let mut file = RawFile::e_try_from(fd)?;
     let data = core::slice::from_raw_parts(buf as *const u8, count);
+    let count = file.write(data)?;
 
-    match file.write(data) {
-        Ok(amount) => amount.try_into().unwrap(),
-        Err(_) => -1,
-    }
+    CIsizeResult::success(count)
 }
 
 #[no_mangle]
-unsafe extern "C" fn read(fd: c_int, buf: *mut c_void, count: usize) -> isize {
+unsafe extern "C" fn read(fd: c_int, buf: *mut c_void, count: usize) -> CIsizeResult {
     buf.ensure();
 
-    let Ok(mut file) = RawFile::try_from(fd) else {
-        return -1;
-    };
+    let mut file = RawFile::e_try_from(fd)?;
     let data = core::slice::from_raw_parts_mut(buf as *mut u8, count);
+    let count = file.read(data)?;
 
-    match file.read(data) {
-        Ok(amount) => amount.try_into().unwrap(),
-        Err(_) => -1,
-    }
+    CIsizeResult::success(count)
 }
 
 #[no_mangle]
-unsafe extern "C" fn lseek(fd: c_int, offset: off_t, whence: c_int) -> off_t {
-    let Ok(mut file) = RawFile::try_from(fd) else {
-        return -1;
-    };
-    let offset = match whence {
-        SEEK_SET => SeekFrom::Start(offset.try_into().unwrap()),
-        SEEK_CUR => SeekFrom::Current(offset),
-        SEEK_END => SeekFrom::End(offset),
-        _ => {
-            error::set_errno(EINVAL);
-            return -1;
-        }
-    };
-
-    match file.seek(offset) {
-        Ok(pos) => pos.try_into().unwrap(),
-        Err(_) => -1,
-    }
+unsafe extern "C" fn lseek(fd: c_int, offset: off_t, whence: c_int) -> COffsetResult {
+    let mut file = RawFile::e_try_from(fd)?;
+    let offset = seek_offset(whence, offset)?;
+    let pos = file.seek(offset)?;
+    COffsetResult::success(pos)
 }
 
 #[no_mangle]
@@ -102,22 +89,22 @@ unsafe extern "C" fn faccessat(
     path: *const c_char,
     amode: c_int,
     flags: c_int,
-) -> c_int {
+) -> CIntZeroResult {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn access(path: *const c_char, amode: c_int) -> c_int {
+unsafe extern "C" fn access(path: *const c_char, amode: c_int) -> CIntZeroResult {
     faccessat(AT_FDCWD, path, amode, 0)
 }
 
 #[no_mangle]
-unsafe extern "C" fn dup(fd: c_int) -> c_int {
+unsafe extern "C" fn dup(fd: c_int) -> CFdResult {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn dup2(oldfd: c_int, newfd: c_int) -> c_int {
+unsafe extern "C" fn dup2(oldfd: c_int, newfd: c_int) -> CFdResult {
     todo!()
 }
 
@@ -127,17 +114,17 @@ unsafe extern "C" fn isatty(fd: c_int) -> c_int {
 }
 
 #[no_mangle]
-unsafe extern "C" fn rmdir(pathname: *const c_char) -> c_int {
+unsafe extern "C" fn rmdir(pathname: *const c_char) -> CIntZeroResult {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn chdir(pathname: *const c_char) -> c_int {
+unsafe extern "C" fn chdir(pathname: *const c_char) -> CIntZeroResult {
     todo!()
 }
 
 #[no_mangle]
-unsafe extern "C" fn pipe(fds: *mut c_int) -> c_int {
+unsafe extern "C" fn pipe(fds: *mut c_int) -> CIntZeroResult {
     todo!()
 }
 
diff --git a/src/header/unistd/process.rs b/src/header/unistd/process.rs
index 2e0e924..639847e 100644
--- a/src/header/unistd/process.rs
+++ b/src/header/unistd/process.rs
@@ -7,21 +7,22 @@ use alloc::{vec, vec::Vec};
 use yggdrasil_rt::{path::Path, process::ExecveOptions, sys as syscall};
 
 use crate::{
-    error::{CZeroResult, EResult},
-    header::{errno::Errno, sys_types::pid_t},
+    error::{CIntZeroResult, CPidResult, EResult},
+    header::sys_types::pid_t,
+    process,
     util::{self, NullTerminated},
 };
 
-unsafe fn fork_inner() -> Result<pid_t, Errno> {
-    let result = EResult::from(syscall::fork())?;
-    Ok(result as _)
+unsafe fn fork_inner() -> EResult<u32> {
+    let result = syscall::fork()?;
+    EResult::Ok(result)
 }
 
 // TODO error reporting
 unsafe fn collect_execve_args<'a, 'e>(
     argv: *const *mut c_char,
     envp: *const *mut c_char,
-) -> Result<(Vec<&'a str>, Vec<&'e str>), Errno> {
+) -> EResult<(Vec<&'a str>, Vec<&'e str>)> {
     let mut arg_list = vec![];
     let mut env_list = vec![];
 
@@ -38,34 +39,28 @@ unsafe fn collect_execve_args<'a, 'e>(
         }
     }
 
-    Ok((arg_list, env_list))
+    EResult::Ok((arg_list, env_list))
 }
 
-unsafe fn execve_inner<P: AsRef<Path>>(
-    pathname: P,
-    argv: &[&str],
-    envp: &[&str],
-) -> Result<(), Errno> {
+unsafe fn execve_inner<P: AsRef<Path>>(pathname: P, argv: &[&str], envp: &[&str]) -> EResult<()> {
     let opts = ExecveOptions {
         program: pathname.as_ref().as_str(),
         arguments: argv,
         environment: envp,
     };
-    let result = EResult::from(syscall::execve(&opts))?;
-    Ok(result as _)
+    let result = syscall::execve(&opts)?;
+    EResult::Ok(result)
 }
 
-unsafe fn execvpe_inner(file: &str, argv: &[&str], envp: &[&str]) -> Result<(), Errno> {
+unsafe fn execvpe_inner(file: &str, argv: &[&str], envp: &[&str]) -> EResult<()> {
     let pathname = util::resolve_binary(file)?;
     execve_inner(&pathname, argv, envp)
 }
 
 #[no_mangle]
-unsafe extern "C" fn fork() -> pid_t {
-    match fork_inner() {
-        Ok(pid) => pid,
-        Err(_) => -1,
-    }
+unsafe extern "C" fn fork() -> CPidResult {
+    let pid = fork_inner()?;
+    CPidResult::success(pid)
 }
 
 #[no_mangle]
@@ -73,27 +68,26 @@ unsafe extern "C" fn execve(
     pathname: *const c_char,
     argv: *const *mut c_char,
     envp: *const *mut c_char,
-) -> c_int {
+) -> CIntZeroResult {
     if pathname.is_null() {
         panic!();
     }
     let pathname = CStr::from_ptr(pathname);
     let pathname = pathname.to_str().unwrap();
-    let (argv, envp) = match collect_execve_args(argv, envp) {
-        Ok(r) => r,
-        Err(_) => return -1,
-    };
+    let (argv, envp) = collect_execve_args(argv, envp)?;
 
-    execve_inner(pathname, &argv, &envp).into_zero_status()
+    execve_inner(pathname, &argv, &envp)?;
+
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
-unsafe extern "C" fn execv(pathname: *const c_char, argv: *const *mut c_char) -> c_int {
+unsafe extern "C" fn execv(pathname: *const c_char, argv: *const *mut c_char) -> CIntZeroResult {
     execve(pathname, argv, null())
 }
 
 #[no_mangle]
-unsafe extern "C" fn execvp(file: *const c_char, argv: *const *mut c_char) -> c_int {
+unsafe extern "C" fn execvp(file: *const c_char, argv: *const *mut c_char) -> CIntZeroResult {
     execvpe(file, argv, null())
 }
 
@@ -102,18 +96,17 @@ unsafe extern "C" fn execvpe(
     file: *const c_char,
     argv: *const *mut c_char,
     envp: *const *mut c_char,
-) -> c_int {
+) -> CIntZeroResult {
     if file.is_null() {
         panic!();
     }
     let file = CStr::from_ptr(file);
     let file = file.to_str().unwrap();
-    let (argv, envp) = match collect_execve_args(argv, envp) {
-        Ok(r) => r,
-        Err(_) => return -1,
-    };
+    let (argv, envp) = collect_execve_args(argv, envp)?;
 
-    execvpe_inner(file, &argv, &envp).into_zero_status()
+    execvpe_inner(file, &argv, &envp)?;
+
+    CIntZeroResult::OK
 }
 
 #[no_mangle]
@@ -123,6 +116,6 @@ unsafe extern "C" fn _exit(status: c_int) -> ! {
 
 #[no_mangle]
 unsafe extern "C" fn getpid() -> pid_t {
-    let pid = syscall::get_pid();
+    let pid = process::current_pid();
     pid.try_into().unwrap()
 }
diff --git a/src/io/buffered.rs b/src/io/buffered.rs
index f70c1ff..7493a6f 100644
--- a/src/io/buffered.rs
+++ b/src/io/buffered.rs
@@ -6,7 +6,7 @@ use core::{
 
 use alloc::{boxed::Box, vec::Vec};
 
-use crate::header::errno::Errno;
+use crate::error::EResult;
 
 use super::{Read, Write};
 
@@ -65,20 +65,20 @@ impl<'a> ReadBuffer<'a> {
         self.len = 0;
     }
 
-    pub fn fill_from<R: Read + ?Sized>(&mut self, source: &mut R) -> Result<&[u8], Errno> {
+    pub fn fill_from<R: Read + ?Sized>(&mut self, source: &mut R) -> EResult<&[u8]> {
         let buffer = unsafe { self.data.as_slice_mut() };
         if self.position == self.len {
             let amount = match source.read(buffer) {
-                Ok(0) => return Ok(&buffer[..0]),
-                Ok(n) => n,
-                Err(err) => return Err(err),
+                EResult::Ok(0) => return EResult::Ok(&buffer[..0]),
+                EResult::Ok(n) => n,
+                EResult::Err(err) => return EResult::Err(err),
             };
 
             self.position = 0;
             self.len = amount;
         }
 
-        Ok(&mut buffer[self.position..self.len])
+        EResult::Ok(&mut buffer[self.position..self.len])
     }
 
     pub fn consume(&mut self, amount: usize) {
@@ -137,17 +137,17 @@ impl<W: Write> LineWriter<W> {
 }
 
 impl<W: Write> Write for UnbufferedWriter<W> {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno> {
+    fn write(&mut self, data: &[u8]) -> EResult<usize> {
         self.inner.write(data)
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
-        Ok(())
+    fn flush(&mut self) -> EResult<()> {
+        EResult::Ok(())
     }
 }
 
 impl<W: Write> Write for BufWriter<W> {
-    fn write(&mut self, mut data: &[u8]) -> Result<usize, Errno> {
+    fn write(&mut self, mut data: &[u8]) -> EResult<usize> {
         if data.len() + self.buffer.len() >= self.buffer.capacity() {
             self.flush()?;
         }
@@ -169,10 +169,10 @@ impl<W: Write> Write for BufWriter<W> {
         // Store the data in the buffer
         assert!(data.len() < self.buffer.capacity());
         self.buffer.extend_from_slice(data);
-        Ok(len)
+        EResult::Ok(len)
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
+    fn flush(&mut self) -> EResult<()> {
         let (amount, result) = self.inner.write_chunked(&self.buffer);
         if amount != 0 {
             self.buffer.drain(..amount);
@@ -182,7 +182,7 @@ impl<W: Write> Write for BufWriter<W> {
 }
 
 impl<W: Write> Write for LineWriter<W> {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno> {
+    fn write(&mut self, data: &[u8]) -> EResult<usize> {
         if self.need_flush {
             self.flush()?;
         }
@@ -195,20 +195,20 @@ impl<W: Write> Write for LineWriter<W> {
         let amount = self.inner.write(&data[..nl_pos + 1])?;
         self.need_flush = true;
         if self.flush().is_err() || amount != nl_pos + 1 {
-            return Ok(amount);
+            return EResult::Ok(amount);
         }
 
         // Write the rest to the buffer
         match self.inner.write(&data[nl_pos + 1..]) {
-            Ok(amount_to_buffer) => Ok(amount_to_buffer + amount),
-            Err(_) => Ok(amount),
+            EResult::Ok(amount_to_buffer) => EResult::Ok(amount_to_buffer + amount),
+            EResult::Err(_) => EResult::Ok(amount),
         }
     }
 
-    fn flush(&mut self) -> Result<(), Errno> {
+    fn flush(&mut self) -> EResult<()> {
         self.inner.flush()?;
         self.need_flush = false;
-        Ok(())
+        EResult::Ok(())
     }
 }
 
diff --git a/src/io/dir.rs b/src/io/dir.rs
index 07b5e97..19eadcb 100644
--- a/src/io/dir.rs
+++ b/src/io/dir.rs
@@ -7,10 +7,9 @@ use yggdrasil_rt::{
     sys as syscall,
 };
 
-use crate::{
-    error::{self, EResult},
-    header::errno::{Errno, EBADF},
-};
+use crate::{error::EResult, header::errno::EBADF};
+
+use super::FromRawFd;
 
 #[derive(Debug)]
 pub struct DirReader {
@@ -25,27 +24,17 @@ pub struct DirReader {
 impl DirReader {
     const BUFFER_SIZE: usize = 16;
 
-    pub fn open_at<P: AsRef<Path>>(at: Option<RawFd>, path: P) -> Result<Self, Errno> {
-        let fd = EResult::from(unsafe { syscall::open_directory(at, path.as_ref().as_str()) })?;
-        Ok(unsafe { Self::from_raw_fd(fd) })
+    pub fn open_at<P: AsRef<Path>>(at: Option<RawFd>, path: P) -> EResult<Self> {
+        let fd = unsafe { syscall::open_directory(at, path.as_ref().as_str()) }?;
+        EResult::Ok(unsafe { Self::from_raw_fd(fd) })
     }
 
-    pub unsafe fn from_raw_fd(fd: RawFd) -> Self {
-        Self {
-            fd: Some(fd),
-
-            buffer: Box::new_uninit_slice(Self::BUFFER_SIZE),
-            position: 0,
-            len: 0,
-        }
-    }
-
-    pub unsafe fn close(&mut self) -> Result<(), Errno> {
+    pub unsafe fn close(&mut self) -> EResult<()> {
         if let Some(fd) = self.fd.take() {
-            EResult::from(unsafe { syscall::close(fd) })?;
-            Ok(())
+            unsafe { syscall::close(fd) }?;
+            EResult::Ok(())
         } else {
-            error::set_errno_result(EBADF)
+            EResult::Err(EBADF)
         }
     }
 
@@ -53,34 +42,47 @@ impl DirReader {
         self.fd.unwrap()
     }
 
-    fn fill_buf(&mut self) -> Result<&[DirectoryEntry], Errno> {
+    fn fill_buf(&mut self) -> EResult<&[DirectoryEntry]> {
         let Some(fd) = self.fd else {
-            return error::set_errno_result(EBADF);
+            return EResult::Err(EBADF);
         };
 
         if self.position == self.len {
-            let count =
-                EResult::from(unsafe { syscall::read_directory_entries(fd, &mut self.buffer) })?;
+            let count = unsafe { syscall::read_directory_entries(fd, &mut self.buffer) }?;
 
             self.position = 0;
             self.len = count;
         }
 
-        Ok(unsafe { MaybeUninit::slice_assume_init_ref(&self.buffer[self.position..self.len]) })
+        EResult::Ok(unsafe {
+            MaybeUninit::slice_assume_init_ref(&self.buffer[self.position..self.len])
+        })
     }
 
     fn consume(&mut self, count: usize) {
         self.position = (self.position + count).min(self.len);
     }
 
-    pub fn read_entry(&mut self) -> Result<Option<DirectoryEntry>, Errno> {
+    pub fn read_entry(&mut self) -> EResult<Option<DirectoryEntry>> {
         let buf = self.fill_buf()?;
 
         if let Some(&entry) = buf.get(0) {
             self.consume(1);
-            Ok(Some(entry))
+            EResult::Ok(Some(entry))
         } else {
-            Ok(None)
+            EResult::Ok(None)
+        }
+    }
+}
+
+impl FromRawFd for DirReader {
+    unsafe fn from_raw_fd(fd: RawFd) -> Self {
+        Self {
+            fd: Some(fd),
+
+            buffer: Box::new_uninit_slice(Self::BUFFER_SIZE),
+            position: 0,
+            len: 0,
         }
     }
 }
diff --git a/src/io/mod.rs b/src/io/mod.rs
index 08d0098..8e16ea0 100644
--- a/src/io/mod.rs
+++ b/src/io/mod.rs
@@ -8,54 +8,62 @@ use yggdrasil_rt::{
 
 use crate::{
     error::EResult,
-    header::errno::{Errno, EINTR},
+    header::errno::{EINTR, ESUCCESS},
 };
 
 pub mod buffered;
 pub mod dir;
 
 pub trait Write {
-    fn write(&mut self, data: &[u8]) -> Result<usize, Errno>;
-    fn flush(&mut self) -> Result<(), Errno>;
+    fn write(&mut self, data: &[u8]) -> EResult<usize>;
+    fn flush(&mut self) -> EResult<()>;
 
-    fn write_chunked(&mut self, data: &[u8]) -> (usize, Result<(), Errno>) {
+    fn write_chunked(&mut self, data: &[u8]) -> (usize, EResult<()>) {
         let mut pos = 0;
         let len = data.len();
 
         while pos < len {
             match self.write(data) {
-                Ok(0) => todo!(),
-                Ok(n) => pos += n,
-                Err(err) if err == EINTR => todo!(),
-                Err(err) => return (pos, Err(err)),
+                EResult::Ok(0) => todo!(),
+                EResult::Ok(n) => pos += n,
+                EResult::Err(err) if err == EINTR => todo!(),
+                EResult::Err(err) => return (pos, EResult::Err(err)),
             }
         }
 
-        (pos, Ok(()))
+        (pos, EResult::Ok(()))
     }
 
-    fn write_all(&mut self, data: &[u8]) -> Result<(), Errno> {
+    fn write_all(&mut self, data: &[u8]) -> EResult<()> {
         match self.write(data) {
-            Ok(n) if n == data.len() => Ok(()),
-            Ok(_) => todo!(), // TODO handle partial writes in write_all
-            Err(err) => Err(err),
+            EResult::Ok(n) if n == data.len() => EResult::Ok(()),
+            EResult::Ok(_) => todo!(), // TODO handle partial writes in write_all
+            EResult::Err(err) => EResult::Err(err),
         }
     }
 }
 
 pub trait Read {
-    fn read(&mut self, data: &mut [u8]) -> Result<usize, Errno>;
+    fn read(&mut self, data: &mut [u8]) -> EResult<usize>;
+
+    fn read_exact(&mut self, data: &mut [u8]) -> EResult<()> {
+        if self.read(data)? == data.len() {
+            EResult::Ok(())
+        } else {
+            EResult::Err(ESUCCESS)
+        }
+    }
 }
 
 pub trait BufRead {
-    fn fill_buf(&mut self) -> Result<&[u8], Errno>;
+    fn fill_buf(&mut self) -> EResult<&[u8]>;
     fn consume(&mut self, amount: usize);
 }
 
 pub trait Seek {
-    fn seek(&mut self, off: SeekFrom) -> Result<u64, Errno>;
+    fn seek(&mut self, off: SeekFrom) -> EResult<u64>;
 
-    fn stream_position(&mut self) -> Result<u64, Errno> {
+    fn stream_position(&mut self) -> EResult<u64> {
         self.seek(SeekFrom::Current(0))
     }
 }
@@ -76,21 +84,13 @@ pub trait IntoRawFd {
     fn into_raw_fd(self) -> RawFd;
 }
 
-pub fn get_metadata<P: AsRef<Path>>(
-    at: Option<RawFd>,
-    path: P,
-    follow: bool,
-) -> Result<FileAttr, Errno> {
+pub fn get_metadata<P: AsRef<Path>>(at: Option<RawFd>, path: P, follow: bool) -> EResult<FileAttr> {
     let mut attr = MaybeUninit::uninit();
-    EResult::from(unsafe { syscall::get_metadata(at, path.as_ref().as_str(), &mut attr, follow) })?;
-    Ok(unsafe { attr.assume_init() })
+    unsafe { syscall::get_metadata(at, path.as_ref().as_str(), &mut attr, follow) }?;
+    EResult::Ok(unsafe { attr.assume_init() })
 }
 
-pub fn create_directory<P: AsRef<Path>>(
-    at: Option<RawFd>,
-    path: P,
-    mode: FileMode,
-) -> Result<(), Errno> {
-    EResult::from(unsafe { syscall::create_directory(at, path.as_ref().as_str(), mode) })?;
-    Ok(())
+pub fn create_directory<P: AsRef<Path>>(at: Option<RawFd>, path: P, mode: FileMode) -> EResult<()> {
+    unsafe { syscall::create_directory(at, path.as_ref().as_str(), mode) }?;
+    EResult::Ok(())
 }
diff --git a/src/lib.rs b/src/lib.rs
index 13cf630..3d5d33d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -8,7 +8,9 @@
     new_uninit,
     maybe_uninit_slice,
     inline_const,
-    vec_into_raw_parts
+    vec_into_raw_parts,
+    slice_ptr_get,
+    strict_provenance
 )]
 #![no_std]
 
diff --git a/src/path.rs b/src/path.rs
index 4b77be6..eea8326 100644
--- a/src/path.rs
+++ b/src/path.rs
@@ -3,10 +3,10 @@ use core::{borrow::Borrow, mem::MaybeUninit, ops::Deref};
 use alloc::{borrow::ToOwned, string::String};
 use yggdrasil_rt::{io::FileAttr, path::Path, sys as syscall};
 
-use crate::{error::EResult, header::errno::Errno};
+use crate::error::EResult;
 
 pub trait PathExt {
-    fn metadata(&self) -> Result<FileAttr, Errno>;
+    fn metadata(&self) -> EResult<FileAttr>;
 
     fn exists(&self) -> bool {
         self.metadata().is_ok()
@@ -17,11 +17,11 @@ pub trait PathExt {
 pub struct PathBuf(String);
 
 impl PathExt for Path {
-    fn metadata(&self) -> Result<FileAttr, Errno> {
+    fn metadata(&self) -> EResult<FileAttr> {
         let mut metadata = MaybeUninit::uninit();
-        EResult::from(unsafe { syscall::get_metadata(None, self.as_str(), &mut metadata, true) })?;
+        unsafe { syscall::get_metadata(None, self.as_str(), &mut metadata, true) }?;
         let metadata = unsafe { metadata.assume_init() };
-        Ok(metadata)
+        EResult::Ok(metadata)
     }
 }
 
diff --git a/src/process.rs b/src/process.rs
index 2e36197..4cd789e 100644
--- a/src/process.rs
+++ b/src/process.rs
@@ -7,9 +7,9 @@ use yggdrasil_rt::{
 };
 
 use crate::{
-    error,
+    error::{EResult, OptionExt},
     header::{
-        errno::{Errno, EINVAL, ENOMEM, ESUCCESS},
+        errno::{EINVAL, ENOMEM, ESUCCESS},
         stdio,
         unistd::environ,
     },
@@ -40,13 +40,14 @@ const ATEXIT_MAX: usize = 32;
 static ATEXIT: Mutex<[Option<extern "C" fn()>; ATEXIT_MAX]> =
     Mutex::new([const { None }; ATEXIT_MAX]);
 
-pub unsafe fn register_atexit(f: extern "C" fn()) -> Result<(), Errno> {
+pub unsafe fn register_atexit(f: extern "C" fn()) -> EResult<()> {
     let mut lock = ATEXIT.lock();
     let Some(slot) = lock.iter_mut().find(|p| p.is_none()) else {
-        return error::set_errno_result(ENOMEM);
+        return EResult::Err(ENOMEM);
     };
+
     slot.replace(f);
-    Ok(())
+    EResult::Ok(())
 }
 
 pub unsafe fn raw_exit<T: ToExitCode>(code: T) -> ! {
@@ -118,26 +119,28 @@ pub fn getenv(name: &str) -> Option<&'static str> {
 }
 
 // NOTE guaranteed to be null-terminated, as the slice is backed by a CString
-pub unsafe fn getenv_raw(key: &[u8]) -> Option<&'static [u8]> {
+pub unsafe fn getenv_raw(key: &[u8]) -> EResult<&'static [u8]> {
     debug_assert_eq!(ENVS.len() + 1, C_ENVS.len());
 
-    ENVS.iter().find_map(|var| {
-        let var = var.as_bytes();
-        let eq_pos = memchr::memchr(b'=', var)?;
-        let var_key = &var[..eq_pos];
-        let var_value = &var[eq_pos + 1..];
+    ENVS.iter()
+        .find_map(|var| {
+            let var = var.as_bytes();
+            let eq_pos = memchr::memchr(b'=', var)?;
+            let var_key = &var[..eq_pos];
+            let var_value = &var[eq_pos + 1..];
 
-        (var_key == key).then_some(var_value)
-    })
+            (var_key == key).then_some(var_value)
+        })
+        .e_ok_or(ESUCCESS)
 }
 
 // TODO test this crap works at all
-pub unsafe fn setenv_raw(key: &[u8], value: Option<&[u8]>, overwrite: bool) -> Result<(), Errno> {
+pub unsafe fn setenv_raw(key: &[u8], value: Option<&[u8]>, overwrite: bool) -> EResult<()> {
     // TODO even though char **environ exists, can this still be put under a lock?
     debug_assert_eq!(ENVS.len() + 1, C_ENVS.len());
 
     if memchr::memchr(b'=', key).is_some() {
-        return error::set_errno_result(EINVAL);
+        return EResult::Err(EINVAL);
     }
 
     let index = ENVS.iter().position(|var| {
@@ -154,7 +157,7 @@ pub unsafe fn setenv_raw(key: &[u8], value: Option<&[u8]>, overwrite: bool) -> R
     if let Some(index) = index {
         if !overwrite {
             // errno is not set
-            return error::set_errno_result(ESUCCESS);
+            return EResult::Err(ESUCCESS);
         }
 
         // Remove the old var
@@ -162,7 +165,7 @@ pub unsafe fn setenv_raw(key: &[u8], value: Option<&[u8]>, overwrite: bool) -> R
         ENVS.remove(index);
     } else if value.is_none() {
         // No entry exists and unsetenv was called
-        return error::set_errno_result(ESUCCESS);
+        return EResult::Err(ESUCCESS);
     }
 
     if let Some(value) = value {
@@ -181,5 +184,5 @@ pub unsafe fn setenv_raw(key: &[u8], value: Option<&[u8]>, overwrite: bool) -> R
         C_ENVS.push(null_mut());
     }
 
-    Ok(())
+    EResult::Ok(())
 }
diff --git a/src/signal.rs b/src/signal.rs
index 8b6444a..f252c1d 100644
--- a/src/signal.rs
+++ b/src/signal.rs
@@ -8,10 +8,7 @@ use yggdrasil_rt::{
 
 use crate::{
     error::EResult,
-    header::{
-        errno::Errno,
-        signal::{sig_handler_t, SigNumber},
-    },
+    header::signal::{sig_handler_t, SigNumber},
     process,
 };
 
@@ -55,9 +52,9 @@ pub unsafe fn set_handler(signal: Signal, handler: Option<sig_handler_t>) -> sig
     core::mem::transmute(old_handler_ptr)
 }
 
-pub unsafe fn send(target: u32, signal: Signal) -> Result<(), Errno> {
-    EResult::from(syscall::send_signal(target, signal))?;
-    Ok(())
+pub unsafe fn send(target: u32, signal: Signal) -> EResult<()> {
+    syscall::send_signal(target, signal)?;
+    EResult::Ok(())
 }
 
 pub unsafe fn init() {
diff --git a/src/util.rs b/src/util.rs
index 37223e9..47dbb49 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,10 +1,19 @@
-use core::{ffi::c_char, fmt, marker::PhantomData, ptr::NonNull, time::Duration};
+use core::{
+    ffi::{c_char, c_int},
+    fmt,
+    marker::PhantomData,
+    ptr::NonNull,
+    time::Duration,
+};
 
-use yggdrasil_rt::{path::Path, sys as syscall};
+use yggdrasil_rt::{io::RawFd, path::Path, sys as syscall};
 
 use crate::{
     error::{EResult, OptionExt},
-    header::errno::Errno,
+    header::{
+        errno::{EBADF, EEXIST},
+        fcntl::AT_FDCWD,
+    },
     path::{PathBuf, PathExt},
     process::getenv,
 };
@@ -20,6 +29,12 @@ pub trait Nullable {
     fn ensure(&self);
 }
 
+pub trait NonNullExt {
+    // TODO added in later versions of Rust
+    unsafe fn add_ext(self, n: usize) -> Self;
+    unsafe fn sub_ext(self, n: usize) -> Self;
+}
+
 pub struct NullTerminated<'a, T: Nullable> {
     data: *const T,
     _pd: PhantomData<&'a ()>,
@@ -105,12 +120,22 @@ impl fmt::Write for CStringWriter {
     }
 }
 
+impl<T> NonNullExt for NonNull<T> {
+    unsafe fn add_ext(self, n: usize) -> Self {
+        Self::new_unchecked(self.as_ptr().add(n))
+    }
+
+    unsafe fn sub_ext(self, n: usize) -> Self {
+        Self::new_unchecked(self.as_ptr().sub(n))
+    }
+}
+
 pub fn resolve_binary<P: AsRef<Path>>(name: P) -> EResult<PathBuf> {
     let name = name.as_ref();
     if name.is_absolute() {
         return EResult::Ok(PathBuf::from(name));
     }
-    let env_path = getenv("PATH").e_ok_or(yggdrasil_rt::Error::DoesNotExist)?;
+    let env_path = getenv("PATH").e_ok_or(EEXIST)?;
 
     for el in env_path.split(':') {
         let path = PathBuf::from_str(el).join(name);
@@ -119,14 +144,22 @@ pub fn resolve_binary<P: AsRef<Path>>(name: P) -> EResult<PathBuf> {
         }
     }
 
-    EResult::Err(yggdrasil_rt::Error::DoesNotExist)
+    EResult::Err(EEXIST)
 }
 
 // TODO EINTR for interrupted sleeps
-pub fn nanosleep(amount: Duration, remaining: Option<&mut Duration>) -> Result<(), Errno> {
+pub fn nanosleep(amount: Duration, remaining: Option<&mut Duration>) -> EResult<()> {
     if remaining.is_some() {
         todo!();
     }
     unsafe { syscall::nanosleep(amount) };
-    Ok(())
+    EResult::Ok(())
+}
+
+pub fn at_fd(fd: c_int) -> EResult<Option<RawFd>> {
+    match fd {
+        AT_FDCWD => EResult::Ok(None),
+        0.. => EResult::Ok(Some(RawFd(fd.try_into().unwrap()))),
+        _ => EResult::Err(EBADF),
+    }
 }