diff --git a/include/bits/stdio.h b/include/bits/stdio.h
index 0103f3e..b07c035 100644
--- a/include/bits/stdio.h
+++ b/include/bits/stdio.h
@@ -11,4 +11,9 @@ int scanf(const char *format, ...);
 int sscanf(const char *str, const char *format, ...);
 int fscanf(FILE *stream, const char *format, ...);
 
+#define P_tmpdir "/tmp"
+
+#define FILENAME_MAX PATH_MAX
+#define FOPEN_MAX OPEN_MAX
+
 #endif
diff --git a/src/header/limits/cbindgen.toml b/src/header/limits/cbindgen.toml
new file mode 100644
index 0000000..266c02a
--- /dev/null
+++ b/src/header/limits/cbindgen.toml
@@ -0,0 +1,13 @@
+language = "C"
+style = "Type"
+
+sys_includes = ["stddef.h", "stdint.h"]
+no_includes = true
+
+include_guard = "_LIMITS_H"
+
+usize_type = "size_t"
+isize_type = "ssize_t"
+
+[export]
+include = []
diff --git a/src/header/limits/mod.rs b/src/header/limits/mod.rs
new file mode 100644
index 0000000..304e4a4
--- /dev/null
+++ b/src/header/limits/mod.rs
@@ -0,0 +1,19 @@
+// TODO take from yggdrasil-abi
+
+pub const FILESIZEBITS: usize = 64;
+pub const MAX_CANON: usize = 64;
+pub const LINK_MAX: usize = 4096;
+pub const NAME_MAX: usize = 255;
+pub const PATH_MAX: usize = 4096;
+
+pub const SYMLINK_MAX: usize = 4096;
+
+pub const PIPE_BUF: usize = 4096;
+
+pub const OPEN_MAX: u32 = u32::MAX - 1;
+pub const STREAM_MAX: u32 = OPEN_MAX;
+
+pub const PAGESIZE: usize = 4096;
+pub const PAGE_SIZE: usize = PAGESIZE;
+
+pub const ATEXIT_MAX: usize = 32;
diff --git a/src/header/mod.rs b/src/header/mod.rs
index 6c9bbeb..68052e0 100644
--- a/src/header/mod.rs
+++ b/src/header/mod.rs
@@ -4,6 +4,7 @@ pub mod sys_types;
 pub mod sys_wait;
 
 pub mod errno;
+pub mod limits;
 pub mod locale;
 pub mod math;
 pub mod stdio;
diff --git a/src/header/stdio/cbindgen.toml b/src/header/stdio/cbindgen.toml
index bc66c65..d6a494f 100644
--- a/src/header/stdio/cbindgen.toml
+++ b/src/header/stdio/cbindgen.toml
@@ -1,7 +1,7 @@
 language = "C"
 style = "Type"
 
-sys_includes = ["stdarg.h", "stddef.h", "stdint.h", "sys/types.h"]
+sys_includes = ["stdarg.h", "stddef.h", "stdint.h", "sys/types.h", "limits.h"]
 no_includes = true
 
 include_guard = "_STDIO_H"
diff --git a/src/header/stdio/file.rs b/src/header/stdio/file.rs
index 700ac71..b2fdc6e 100644
--- a/src/header/stdio/file.rs
+++ b/src/header/stdio/file.rs
@@ -43,6 +43,11 @@ fn open_inner<O: FileOpenSource>(source: O, mode_str: &[u8]) -> Result<*mut FILE
     }
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn ctermid(buffer: *mut c_char) -> *mut c_char {
+    todo!()
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn fopen(pathname: *const c_char, mode: *const c_char) -> *mut FILE {
     if pathname.is_null() || mode.is_null() {
@@ -52,10 +57,26 @@ 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);
 
-    match open_inner(Path::from_str(pathname), mode.to_bytes()) {
-        Ok(file) => file,
-        Err(_) => null_mut(),
+    open_inner(Path::from_str(pathname), mode.to_bytes()).unwrap_or(null_mut())
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fdopen(fd: c_int, mode: *const c_char) -> *mut 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())
+}
+
+#[no_mangle]
+unsafe extern "C" fn freopen(
+    pathname: *const c_char,
+    mode: *const c_char,
+    stream: *mut FILE,
+) -> *mut FILE {
+    todo!()
 }
 
 #[no_mangle]
@@ -229,3 +250,53 @@ pub unsafe extern "C" fn setbuffer(stream: *mut FILE, buf: *mut c_char, size: us
 pub unsafe extern "C" fn setlinebuf(stream: *mut FILE) {
     setvbuf(stream, null_mut(), _IOLBF, 0);
 }
+
+#[no_mangle]
+unsafe extern "C" fn fmemopen(buffer: *mut c_void, size: usize, mode: *mut c_char) -> *mut FILE {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn open_memstream(bufptr: *mut *mut c_char, sizeptr: *mut usize) -> *mut FILE {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn popen(command: *const c_char, mode: *const c_char) -> *mut FILE {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn pclose(stream: *mut FILE) -> c_int {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn remove(pathname: *const c_char) -> c_int {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn rename(oldname: *const c_char, newname: *const c_char) -> c_int {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn renameat(fd: c_int, oldname: *const c_char, newname: *const c_char) -> c_int {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn tempnam(dir: *const c_char, pfx: *const c_char) -> *mut c_char {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn tmpfile() -> *mut FILE {
+    todo!()
+}
+
+#[no_mangle]
+unsafe extern "C" fn tmpnam(template: *mut c_char) -> *mut c_char {
+    todo!()
+}
diff --git a/src/header/stdio/get_put.rs b/src/header/stdio/get_put.rs
index 52d228c..0513c05 100644
--- a/src/header/stdio/get_put.rs
+++ b/src/header/stdio/get_put.rs
@@ -4,11 +4,32 @@ use core::{
 };
 
 use crate::{
-    header::stdlib::realloc,
+    error,
+    header::{stdlib::realloc, string::strlen},
     io::{Read, Write},
 };
 
-use super::{stdin, stdout, EOF, FILE};
+use super::{
+    stderr, stdin, stdout,
+    unlocked::{flockfile, fputc_unlocked, fputs_unlocked, funlockfile, fwrite_unlocked},
+    EOF, FILE,
+};
+
+#[no_mangle]
+unsafe extern "C" fn perror(msg: *const c_char) {
+    flockfile(stderr);
+
+    if !msg.is_null() {
+        fputs_unlocked(msg, stderr);
+        fputc_unlocked(b':' as _, stderr);
+        fputc_unlocked(b' ' as _, stderr);
+    }
+
+    fputs_unlocked(error::errno.to_c_str(), stderr);
+    fputc_unlocked(b'\n' as _, stderr);
+
+    funlockfile(stderr);
+}
 
 // Chars
 
diff --git a/src/header/stdio/mod.rs b/src/header/stdio/mod.rs
index fb59d08..00b7c1e 100644
--- a/src/header/stdio/mod.rs
+++ b/src/header/stdio/mod.rs
@@ -20,45 +20,11 @@ use crate::{
     sync::{Mutex, RawMutex},
 };
 
-use super::errno::Errno;
+use super::{errno::Errno, limits};
 
 // TODO:
 // L_ctermid
 // L_tmpnam
-//
-// SEEK_CUR
-// SEEK_END
-// SEEK_SET
-//
-// FILENAME_MAX
-// FOPEN_MAX
-// TMP_MAX
-//
-// EOF
-//
-// P_tmpdir
-
-/*
-char    *ctermid(char *);
-FILE    *fdopen(int, const char *);
-void     flockfile(FILE *);
-FILE    *fmemopen(void *restrict, size_t, const char *restrict);
-FILE    *freopen(const char *restrict, const char *restrict,
-             FILE *restrict);
-int      ftrylockfile(FILE *);
-void     funlockfile(FILE *);
-FILE    *open_memstream(char **, size_t *);
-int      pclose(FILE *);
-void     perror(const char *);
-FILE    *popen(const char *, const char *);
-int      remove(const char *);
-int      rename(const char *, const char *);
-int      renameat(int, const char *, int, const char *);
-char    *tempnam(const char *, const char *);
-FILE    *tmpfile(void);
-char    *tmpnam(char *);
-
-*/
 
 macro_rules! locked_op {
     ($self:expr, $op:expr) => {{
@@ -139,12 +105,16 @@ impl FILE {
         }
     }
 
-    pub unsafe fn new_builtin(fd: RawFd, flags: FileFlags) -> Self {
+    pub unsafe fn new_builtin(fd: RawFd, flags: FileFlags, buffered: bool) -> Self {
         let inner = FileBacking::File(File::new(fd));
         Self {
             lock: RawMutex::new(),
 
-            output: Box::new(LineWriter::with_capacity(inner.make_ref(), BUFSIZ)),
+            output: if buffered {
+                Box::new(LineWriter::with_capacity(inner.make_ref(), BUFSIZ))
+            } else {
+                Box::new(UnbufferedWriter::new(inner.make_ref()))
+            },
             inner,
             read_buffer: Some(ReadBuffer::owned(BUFSIZ)),
 
@@ -261,22 +231,22 @@ impl FILE {
         }
     }
 
-    unsafe fn ungetc_unlocked(&mut self, ch: u8) -> bool {
-        // ungetc() for write doesn't make any sense
-        if self.set_direction(Direction::Read).is_err() {
-            return false;
-        }
-        if self.ungetc.len() == UNGETC_MAX {
-            return false;
-        }
-        self.ungetc.push(ch);
-        true
-    }
-
     pub fn ungetc(&mut self, ch: u8) -> bool {
         locked_op!(self, self.ungetc_unlocked(ch))
     }
 
+    pub fn lock(&mut self) {
+        self.lock.lock();
+    }
+
+    pub fn try_lock(&mut self) -> bool {
+        self.lock.try_lock()
+    }
+
+    pub unsafe fn unlock(&mut self) {
+        self.lock.release();
+    }
+
     fn reset(&mut self) {
         if let Some(read_buffer) = self.read_buffer.as_mut() {
             read_buffer.reset();
@@ -367,6 +337,18 @@ impl FILE {
             _ => Ok(()),
         }
     }
+
+    unsafe fn ungetc_unlocked(&mut self, ch: u8) -> bool {
+        // ungetc() for write doesn't make any sense
+        if self.set_direction(Direction::Read).is_err() {
+            return false;
+        }
+        if self.ungetc.len() == UNGETC_MAX {
+            return false;
+        }
+        self.ungetc.push(ch);
+        true
+    }
 }
 
 impl fmt::Write for FILE {
@@ -475,6 +457,8 @@ pub const SEEK_SET: c_int = 0;
 pub const SEEK_CUR: c_int = 1;
 pub const SEEK_END: c_int = 2;
 
+pub const TMP_MAX: usize = 216000;
+
 pub const EOF: c_int = -1;
 
 pub type fpos_t = u64;
@@ -494,9 +478,21 @@ pub unsafe fn deregister_file(file: *mut FILE) -> bool {
 }
 
 pub unsafe fn setup_default_files() {
-    let stdin_ = Box::into_raw(Box::new(FILE::new_builtin(RawFd::STDIN, FileFlags::READ)));
-    let stdout_ = Box::into_raw(Box::new(FILE::new_builtin(RawFd::STDOUT, FileFlags::WRITE)));
-    let stderr_ = Box::into_raw(Box::new(FILE::new_builtin(RawFd::STDERR, FileFlags::WRITE)));
+    let stdin_ = Box::into_raw(Box::new(FILE::new_builtin(
+        RawFd::STDIN,
+        FileFlags::READ,
+        true,
+    )));
+    let stdout_ = Box::into_raw(Box::new(FILE::new_builtin(
+        RawFd::STDOUT,
+        FileFlags::WRITE,
+        true,
+    )));
+    let stderr_ = Box::into_raw(Box::new(FILE::new_builtin(
+        RawFd::STDERR,
+        FileFlags::WRITE,
+        false,
+    )));
 
     stdin = stdin_;
     stdout = stdout_;
diff --git a/src/header/stdio/unlocked.rs b/src/header/stdio/unlocked.rs
index d57b8b6..1abbf79 100644
--- a/src/header/stdio/unlocked.rs
+++ b/src/header/stdio/unlocked.rs
@@ -1,10 +1,31 @@
-use core::ffi::{c_int, c_void};
+use core::ffi::{c_char, c_int, c_void, CStr};
 
 use yggdrasil_rt::io::RawFd;
 
 use crate::error::{CSizeResult, CZeroResult};
 
-use super::{FileFlags, FILE};
+use super::{FileFlags, EOF, FILE};
+
+#[no_mangle]
+pub unsafe extern "C" fn flockfile(stream: *mut FILE) {
+    let stream = stream.as_mut().unwrap();
+    stream.lock();
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn ftrylockfile(stream: *mut FILE) -> c_int {
+    let stream = stream.as_mut().unwrap();
+    match stream.try_lock() {
+        true => 0,
+        false => -1,
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn funlockfile(stream: *mut FILE) {
+    let stream = stream.as_mut().unwrap();
+    stream.unlock();
+}
 
 #[no_mangle]
 pub unsafe extern "C" fn feof_unlocked(stream: *mut FILE) -> c_int {
@@ -74,17 +95,46 @@ pub unsafe extern "C" fn fflush_unlocked(stream: *mut FILE) -> c_int {
     }
 }
 
-/*
-int getc_unlocked(FILE *stream);
-int getchar_unlocked(void);
-int putc_unlocked(int c, FILE *stream);
-int putchar_unlocked(int c);
-
-int fgetc_unlocked(FILE *stream);
-int fputc_unlocked(int c, FILE *stream);
-*/
+#[no_mangle]
+pub unsafe extern "C" fn fgetc_unlocked(stream: *mut FILE) -> c_int {
+    todo!()
+}
 
 #[no_mangle]
 pub unsafe extern "C" fn getc_unlocked(stream: *mut FILE) -> c_int {
     todo!()
 }
+
+#[no_mangle]
+pub unsafe extern "C" fn getchar_unlocked() -> c_int {
+    todo!()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn putchar_unlocked(c: c_char) -> c_int {
+    todo!()
+}
+
+#[no_mangle]
+pub unsafe fn fputc_unlocked(c: c_int, stream: *mut FILE) -> c_int {
+    let stream = stream.as_mut().unwrap();
+
+    match stream.write_unlocked(&[c as u8]) {
+        Ok(_) => c,
+        Err(_) => EOF,
+    }
+}
+
+pub unsafe fn fputs_unlocked(s: *const c_char, stream: *mut FILE) -> c_int {
+    if s.is_null() {
+        panic!();
+    }
+
+    let s = CStr::from_ptr(s);
+    let stream = stream.as_mut().unwrap();
+
+    match stream.write_unlocked(s.to_bytes()) {
+        Ok(_) => 0,
+        Err(_) => EOF,
+    }
+}
diff --git a/src/header/string/mod.rs b/src/header/string/mod.rs
index b9264b7..f5923cc 100644
--- a/src/header/string/mod.rs
+++ b/src/header/string/mod.rs
@@ -4,6 +4,6 @@ pub mod mem;
 pub mod str;
 
 extern "C" {
-    fn strlen(s: *const c_char) -> usize;
-    fn memset(a: *mut c_void, c: c_int, n: usize) -> *mut c_void;
+    pub fn strlen(s: *const c_char) -> usize;
+    pub fn memset(a: *mut c_void, c: c_int, n: usize) -> *mut c_void;
 }
diff --git a/src/sync.rs b/src/sync.rs
index dd78b57..7b58ad8 100644
--- a/src/sync.rs
+++ b/src/sync.rs
@@ -29,7 +29,7 @@ impl RawMutex {
         }
     }
 
-    fn try_lock(&self) -> bool {
+    pub fn try_lock(&self) -> bool {
         self.value
             .compare_exchange(
                 Self::UNLOCKED,