From 66acd17bc02a8b3ff6292f1fc499b2712edf91f3 Mon Sep 17 00:00:00 2001
From: David Adam <zanchey@ucc.gu.uwa.edu.au>
Date: Sun, 1 Feb 2015 17:11:44 +0800
Subject: [PATCH] isatty: revert to previous behaviour

This partially reverts commit 60808a4820b1714.
---
 doc_src/isatty.txt          | 14 ++++++++------
 share/functions/isatty.fish | 37 +++++++++++++++++++------------------
 2 files changed, 27 insertions(+), 24 deletions(-)

diff --git a/doc_src/isatty.txt b/doc_src/isatty.txt
index 91e5c9c75..f6ab500e6 100644
--- a/doc_src/isatty.txt
+++ b/doc_src/isatty.txt
@@ -1,15 +1,17 @@
-\section isatty isatty - test if a file or file descriptor is a tty.
+\section isatty isatty - test if a file descriptor is a tty.
 
 \subsection isatty-synopsis Synopsis
 \fish{synopsis}
-isatty [FILE | DEVICE | FILE DESCRIPTOR NUMBER]
+isatty [FILE DESCRIPTOR]
 \endfish
 
 \subsection isatty-description Description
 
-`isatty` tests if a file or file descriptor is a tty. The argument may be in the form of a file path, device, or file descriptor number. Without an argument, `standard input` is implied.
+`isatty` tests if a file descriptor is a tty.
 
-If the resolved file descriptor is a tty, the command returns zero. Otherwise, the command exits one. No messages are printed to standard error.
+`FILE DESCRIPTOR` may be either the number of a file descriptor, or one of the strings `stdin`, `stdout`, or `stderr`.
+
+If the specified file descriptor is a tty, the exit status of the command is zero. Otherwise, the exit status is non-zero. No messages are printed to standard error.
 
 
 \subsection isatty-examples Examples
@@ -20,14 +22,14 @@ From an interactive shell, the commands below exit with a return value of zero:
 isatty
 isatty stdout
 isatty 2
-echo | isatty /dev/fd/1
+echo | isatty 1
 \endfish
 
 And these will exit non-zero:
 
 \fish
 echo | isatty
-isatty /dev/fd/9
+isatty 9
 isatty stdout > file
 isatty 2 2> file
 \endfish
diff --git a/share/functions/isatty.fish b/share/functions/isatty.fish
index f49b3aa4e..d4f2c43e3 100644
--- a/share/functions/isatty.fish
+++ b/share/functions/isatty.fish
@@ -1,27 +1,28 @@
-function isatty -d "Test if a file or file descriptor is a tty."
 
-# Use `command test` because `builtin test` doesn't open the regular fd's.
+function isatty -d "Tests if a file descriptor is a tty"
+	set -l fd 0
+	if count $argv >/dev/null
+		switch $argv[1]
 
-  switch "$argv"
+			case -h --h --he --hel --help
+				__fish_print_help isatty
+				return 0
 
-    case '-h*' '--h*'
-      __fish_print_help isatty
+			case stdin
+				set fd 0
 
-    case ''
-      command test -c /dev/stdin
+			case stdout
+				set fd 1
 
-    case '*'
-      if test -e "$argv" # The eval here is needed for symlinks. Unsure why.
-        command test -c "$argv"; and eval tty 0>"$argv" >/dev/null
+			case stderr
+				set fd 2
 
-      else if test -e /dev/"$argv"
-         command test -c /dev/"$argv"; and tty 0>/dev/"$argv" >/dev/null
+			case '*'
+				set fd $argv[1]
 
-      else if test -e /dev/fd/"$argv"
-         command test -c /dev/fd/"$argv"; and tty 0>/dev/fd/"$argv" >/dev/null
+		end
+	end
+
+	eval "tty 0>&$fd >/dev/null"
 
-      else
-         return 1
-    end
-  end
 end