From 31f44481f3e3fef9b3a92d28ae84a872cf20e3a9 Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Sun, 3 Feb 2019 12:38:03 +0100
Subject: [PATCH] Add /dev/{stdin,stdout,stderr} as symlinks to
 /proc/self/fd/{0,1,2}

Also change /bin/cat to open /dev/stdin if no arguments are provided.
---
 Kernel/sync.sh   | 3 +++
 Userland/cat.cpp | 9 +++------
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Kernel/sync.sh b/Kernel/sync.sh
index 447f40ed3f..bb5a353045 100755
--- a/Kernel/sync.sh
+++ b/Kernel/sync.sh
@@ -13,6 +13,9 @@ mknod mnt/dev/psaux c 10 1
 mknod mnt/dev/ptmx c 5 2
 mkdir mnt/dev/pts
 mknod mnt/dev/gui_events c 66 1
+ln -s /proc/self/fd/0 mnt/dev/stdin
+ln -s /proc/self/fd/1 mnt/dev/stdout
+ln -s /proc/self/fd/2 mnt/dev/stderr
 cp -vR ../Base/* mnt/
 chown -vR 100:100 mnt/users/anon
 cp -v ../Userland/sh mnt/bin/sh
diff --git a/Userland/cat.cpp b/Userland/cat.cpp
index 4a5162a41a..5454d7e982 100644
--- a/Userland/cat.cpp
+++ b/Userland/cat.cpp
@@ -8,13 +8,10 @@
 
 int main(int argc, char** argv)
 {
-    if (argc != 2) {
-        printf("usage: cat <file>\n");
-        return 1;
-    }
-    int fd = open(argv[1], O_RDONLY);
+    const char* input_file = argc > 1 ? argv[1] : "/dev/stdin";
+    int fd = open(input_file, O_RDONLY);
     if (fd == -1) {
-        printf("failed to open %s: %s\n", argv[1], strerror(errno));
+        printf("failed to open %s: %s\n", input_file, strerror(errno));
         return 1;
     }
     for (;;) {