1 files changed, 13 insertions, 0 deletions
diff --git a/userland/libc/stdio/fileno.c b/userland/libc/stdio/fileno.c
new file mode 100644
index 0000000..246cc51
--- /dev/null
+++ b/userland/libc/stdio/fileno.c
@@ -0,0 +1,13 @@
+#include <stdio.h>
+#include <errno.h>
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/functions/fileno.html
+// The fileno() function shall return the integer file descriptor associated
+// with the stream pointed to by stream.
+int fileno(FILE *stream) {
+  if (-1 == stream->fd) {
+    errno = EBADF;
+    return -1;
+  }
+  return stream->fd;
+}