From fc00c656c96528112d05cf0edf8631bd5eaea446 Mon Sep 17 00:00:00 2001
From: Kacper <kacper@mail.openlinux.dev>
Date: Sun, 7 Dec 2025 20:10:31 +0100
Subject: Add build system scaffolding and libc headers

---
 lib/libc/stdio/fileno.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 lib/libc/stdio/fileno.c

(limited to 'lib/libc/stdio/fileno.c')

diff --git a/lib/libc/stdio/fileno.c b/lib/libc/stdio/fileno.c
new file mode 100644
index 00000000..09db0ad5
--- /dev/null
+++ b/lib/libc/stdio/fileno.c
@@ -0,0 +1,20 @@
+#include <io.h>
+#include <errno.h>
+#include <atomic.h>
+#include <stdio.h>
+
+int fileno(FILE *stream)
+{
+	int fd;
+
+	LIBC_LOCK(stream->lock);
+	fd = stream->fd;
+	LIBC_UNLOCK(stream->lock);
+
+	if (fd < 0) {
+		errno = EBADF;
+		return -1;
+	}
+
+	return fd;
+}
-- 
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