From 0de7cd42bcbee458e8c0626ec7bae4fe1a6f3bb3 Mon Sep 17 00:00:00 2001
From: Michael Mikonos <127171689+mknos@users.noreply.github.com>
Date: Mon, 6 Jan 2025 11:18:37 +0800
Subject: [PATCH] tsort: '-' argument is not special

* Standards document does not require that a '-' argument is interpreted as stdin [1]
* Follow BSD semantics and treat '-' as a regular file argument (tested against OpenBSD)

1. https://pubs.opengroup.org/onlinepubs/9699919799/utilities/tsort.html
---
 bin/tsort | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/bin/tsort b/bin/tsort
index c56400ab..e55577df 100755
--- a/bin/tsort
+++ b/bin/tsort
@@ -30,12 +30,8 @@ if (@ARGV) {
     warn "$Program: extra operand '$ARGV[0]'\n";
     usage();
 }
-$file = '-' if (!defined($file));
-
 my $fh;
-if ($file eq '-') {
-    $fh = *STDIN;
-} else {
+if (defined $file) {
     if (-d $file) {
         warn "$Program: '$file' is a directory\n";
         exit EX_FAILURE;
@@ -44,6 +40,8 @@ if ($file eq '-') {
         warn "$Program: '$file': $!\n";
         exit EX_FAILURE;
     }
+} else {
+    $fh = *STDIN;
 }
 
 my %pairs;	# all pairs ($l, $r)
@@ -114,6 +112,7 @@ tsort - topological sort
 =over 2
 
 Does a topological sort of input pairs.
+Input is taken from the standard input if no filename argument is provided.
 
 For a more complete description, see the tsort(1) man page,
 For an explanation of the algorithm,