diff --git a/src/stdio/_scanf.c b/src/stdio/_scanf.c
index 3023ba8..ea7ad8e 100644
--- a/src/stdio/_scanf.c
+++ b/src/stdio/_scanf.c
@@ -1,13 +1,52 @@
 #include <_libc/stdio.h>
+#include <ctype.h>
 #include <stdio.h>
 
 int __libc_vscanf(const char *format,
                   void *ctx,
                   int (*in)(void *ctx),
                   va_list ap) {
-    (void) format;
-    (void) ctx;
-    (void) in;
-    (void) ap;
-    return -1;
+    size_t n_convert = 0;
+    union {
+        uint64_t value_unsigned;
+    } pv;
+    char ch;
+    int ic;
+
+    while ((ch = *format)) {
+        if (isspace(ch)) {
+            // Skip whitespace
+        } else if (ch == '%') {
+            // Conversion spec
+            ch = *++format;
+
+            switch (ch) {
+            case 'u':
+                pv.value_unsigned = 0;
+                while ((ic = in(ctx)) != EOF && isdigit(ic)) {
+                    pv.value_unsigned *= 10;
+                    pv.value_unsigned += ic - '0';
+                }
+                *((unsigned int *) va_arg(ap, unsigned int *)) = pv.value_unsigned;
+                ++n_convert;
+                ++format;
+                break;
+            default:
+                goto err;
+            }
+        } else {
+            ic = in(ctx);
+
+            if (ic == EOF) {
+                goto err;
+            }
+        }
+        ++format;
+    }
+
+err:
+    if (!n_convert) {
+        return -1;
+    }
+    return n_convert;
 }
diff --git a/src/stdio/fgetc_unlocked.c b/src/stdio/fgetc_unlocked.c
index a77dfb2..bcf5535 100644
--- a/src/stdio/fgetc_unlocked.c
+++ b/src/stdio/fgetc_unlocked.c
@@ -12,12 +12,12 @@ int fgetc_unlocked(FILE *fp) {
     }
 
     if (fp->flags & FILE_FLAG_EOF) {
-        return 0;
+        return EOF;
     }
     if (!(fp->flags & FILE_MODE_READ)) {
         errno = EBADF;
         fp->flags |= FILE_FLAG_ERROR;
-        return 0;
+        return EOF;
     }
 
     __libc_file_flush_write(fp);
diff --git a/src/stdio/fgets_unlocked.c b/src/stdio/fgets_unlocked.c
index 3f47a21..fbe2ae0 100644
--- a/src/stdio/fgets_unlocked.c
+++ b/src/stdio/fgets_unlocked.c
@@ -1,3 +1,4 @@
+#include <sys/debug.h>
 #include <stdio.h>
 
 char *fgets_unlocked(char *buf, int len, FILE *fp) {
@@ -23,7 +24,11 @@ char *fgets_unlocked(char *buf, int len, FILE *fp) {
     }
 
     if (off) {
+        ygg_debug_trace("fgets -> %d\n", off);
         buf[off] = 0;
+        for (size_t i = 0; i < off; ++i) {
+            ygg_debug_trace("buf[%d] = 0x%x\n", i, buf[i]);
+        }
         return buf;
     } else {
         return NULL;
diff --git a/src/stdio/file.c b/src/stdio/file.c
index e7baf95..6d19b1f 100644
--- a/src/stdio/file.c
+++ b/src/stdio/file.c
@@ -20,6 +20,7 @@ FILE *__libc_file_create(void) {
 
     res->free = file_default_free;
     res->buf = ((void *) res) + sizeof(FILE);
+    res->ungetc = -1;
 
     return res;
 }
@@ -43,9 +44,8 @@ int __libc_file_mode(const char *mode) {
 }
 
 int __libc_file_flush_read(FILE *fp) {
+    fp->ungetc = -1;
     if ((fp->flags & FILE_MODE_READ) && fp->seek) {
-        // Flush ungetc buffer
-        fp->ungetc = -1;
         // TODO: off_t
         long count = fp->rdbuf - fp->rdbufpos;
         if (count < 0) {
diff --git a/src/stdio/file_file.c b/src/stdio/file_file.c
index 06bcb51..780c47e 100644
--- a/src/stdio/file_file.c
+++ b/src/stdio/file_file.c
@@ -17,6 +17,7 @@ FILE _stdin = {
     .buf_mode = _IOLBF,
     .ctx = &_stdin,
     .fd = STDIN_FILENO,
+    .ungetc = -1,
     .free = NULL,
     .read = file_read,
     .write = file_write,
diff --git a/src/stdio/puts.c b/src/stdio/puts.c
new file mode 100644
index 0000000..bb5b51d
--- /dev/null
+++ b/src/stdio/puts.c
@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+int puts(const char *s) {
+    flockfile(stdout);
+    if (fputs(s, stdout) != 0) {
+        funlockfile(stdout);
+        return EOF;
+    }
+    if (fputc('\n', stdout) == EOF) {
+        funlockfile(stdout);
+        return EOF;
+    }
+    funlockfile(stdout);
+    return 0;
+}