cat: allow copying empty files to themselves

Problem reported by Vincent Lefevre in: http://bugs.gnu.org/18449
* src/cat.c (main): Allow copying an empty file to itself.
* tests/misc/cat-self.sh: New test.
* tests/local.mk (all_tests): Add it.

1 files changed, 33 insertions, 0 deletions

diff --git a/tests/misc/cat-self.sh b/tests/misc/cat-self.sh
new file mode 100755
index 000000000..d8036d235
--- /dev/null
+++ b/tests/misc/cat-self.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+# Check that cat operates correctly when the input is the same as the output.
+
+# Copyright 2014 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ cat
+
+echo x >out || framework_failure_
+echo x >out1 || framework_failure_
+cat out >>out && fail=1
+compare out out1 || fail=1
+
+# This example is taken from the POSIX spec for 'cat'.
+echo x >doc || framework_failure_
+echo y >doc.end || framework_failure_
+cat doc doc.end >doc || fail=1
+compare doc doc.end || fail=1
+
+Exit $fail