From 754112220645222d145da82091d31f7c35d5dc33 Mon Sep 17 00:00:00 2001
From: Sergey Bugaev <bugaevc@serenityos.org>
Date: Tue, 19 May 2020 20:34:45 +0300
Subject: [PATCH] Kernel+LibC: Switch isatty() to use a fcntl()

We would want it to work with only stdio pledged.
---
 Kernel/Process.cpp        | 2 ++
 Kernel/UnixTypes.h        | 1 +
 Libraries/LibC/fcntl.h    | 1 +
 Libraries/LibC/unistd.cpp | 3 +--
 4 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index 393f93a58a3..1320d5ddaef 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -1845,6 +1845,8 @@ int Process::sys$fcntl(int fd, int cmd, u32 arg)
     case F_SETFL:
         description->set_file_flags(arg);
         break;
+    case F_ISTTY:
+        return description->is_tty();
     default:
         return -EINVAL;
     }
diff --git a/Kernel/UnixTypes.h b/Kernel/UnixTypes.h
index a8923b20324..c9197931e94 100644
--- a/Kernel/UnixTypes.h
+++ b/Kernel/UnixTypes.h
@@ -74,6 +74,7 @@
 #define F_SETFD 2
 #define F_GETFL 3
 #define F_SETFL 4
+#define F_ISTTY 5
 
 #define FD_CLOEXEC 1
 
diff --git a/Libraries/LibC/fcntl.h b/Libraries/LibC/fcntl.h
index d56dae85f52..1aa6e6cd09a 100644
--- a/Libraries/LibC/fcntl.h
+++ b/Libraries/LibC/fcntl.h
@@ -36,6 +36,7 @@ __BEGIN_DECLS
 #define F_SETFD 2
 #define F_GETFL 3
 #define F_SETFL 4
+#define F_ISTTY 5
 
 #define FD_CLOEXEC 1
 
diff --git a/Libraries/LibC/unistd.cpp b/Libraries/LibC/unistd.cpp
index 652eaabe43c..ec01ad1be4d 100644
--- a/Libraries/LibC/unistd.cpp
+++ b/Libraries/LibC/unistd.cpp
@@ -413,8 +413,7 @@ int rmdir(const char* pathname)
 
 int isatty(int fd)
 {
-    struct termios dummy;
-    return tcgetattr(fd, &dummy) == 0;
+    return fcntl(fd, F_ISTTY);
 }
 
 int dup(int old_fd)