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authorJim Meyering <meyering@redhat.com>2009-09-07 22:10:10 +0200
committerJim Meyering <meyering@redhat.com>2009-09-07 23:19:56 +0200
commitaf6436559c2954d7f35b7fec29dfcbaa4ebdc03b (patch)
tree4c5d53442d729d663c15809899bd5c03bdf13b6d
parentfd9750b0ffb691d2ad97551eada5c2802df3c805 (diff)
downloadcoreutils-af6436559c2954d7f35b7fec29dfcbaa4ebdc03b.tar.xz
tail: ignore -f for piped-stdin, as POSIX requires
* src/tail.c (main): Tailing a pipe "forever" is not useful, and POSIX specifies that tail ignore the -f when there is no file argument and stdin is a FIFO or pipe. So we do that. In addition, GNU tail excludes "-" arguments from the list of files to tail forever, when the associated file descriptor is connected to a FIFO or pipe. Before this change, ":|tail -f" would hang. Reported by Ren Yang and Ulrich Drepper. * tests/tail-2/pipe-f: Test for this. * tests/tail-2/pipe-f2: Ensure tail doesn't exit early for a fifo. * tests/Makefile.am (TESTS): Add these tests. * NEWS (POSIX conformance): Mention it.
-rw-r--r--NEWS6
-rw-r--r--THANKS1
-rw-r--r--src/tail.c16
-rw-r--r--tests/Makefile.am2
-rwxr-xr-xtests/tail-2/pipe-f32
-rwxr-xr-xtests/tail-2/pipe-f237
6 files changed, 93 insertions, 1 deletions
diff --git a/NEWS b/NEWS
index a5a60948e..7d4f7e203 100644
--- a/NEWS
+++ b/NEWS
@@ -46,6 +46,12 @@ GNU coreutils NEWS -*- outline -*-
cp --reflink accepts a new "auto" parameter which falls back to
a standard copy if creating a copy-on-write clone is not possible.
+** POSIX conformance
+
+ tail -f now ignores "-" when stdin is a pipe or FIFO, per POSIX.
+ Now, :|tail -f terminates immediately. Before, it would block indefinitely.
+ [the old behavior dates back to the original implementation]
+
* Noteworthy changes in release 7.5 (2009-08-20) [stable]
diff --git a/THANKS b/THANKS
index 2410866ae..c6655eb78 100644
--- a/THANKS
+++ b/THANKS
@@ -490,6 +490,7 @@ Ralph Loader loader@maths.ox.ac.uk
Raul Miller moth@magenta.com
Raúl Núñez de Arenas Coronado raul@pleyades.net
Reuben Thomas rrt@sc3d.org
+Ren Yang ryang@redhat.com
Richard A Downing richard.downing@bcs.org.uk
Richard Braakman dark@xs4all.nl
Richard Dawe rich@phekda.freeserve.co.uk
diff --git a/src/tail.c b/src/tail.c
index 9288007ca..d75d9b3e4 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -1979,7 +1979,21 @@ main (int argc, char **argv)
for (i = 0; i < n_files; i++)
ok &= tail_file (&F[i], n_units);
- if (forever)
+ /* When there is no FILE operand and stdin is a pipe or FIFO
+ POSIX requires that tail ignore the -f option.
+ Since we allow multiple FILE operands, we extend that to say:
+ ignore any "-" operand that corresponds to a pipe or FIFO. */
+ size_t n_viable = 0;
+ for (i = 0; i < n_files; i++)
+ {
+ if (STREQ (F[i].name, "-") && !F[i].ignore
+ && 0 <= F[i].fd && S_ISFIFO (F[i].mode))
+ F[i].ignore = true;
+ else
+ ++n_viable;
+ }
+
+ if (forever && n_viable)
{
#if HAVE_INOTIFY
/* If the user specifies stdin via a command line argument of "-",
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 6b3c2b149..42a12cfac 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -429,6 +429,8 @@ TESTS = \
tail-2/big-4gb \
tail-2/flush-initial \
tail-2/follow-stdin \
+ tail-2/pipe-f \
+ tail-2/pipe-f2 \
tail-2/proc-ksyms \
tail-2/start-middle \
touch/dangling-symlink \
diff --git a/tests/tail-2/pipe-f b/tests/tail-2/pipe-f
new file mode 100755
index 000000000..b9f6ae389
--- /dev/null
+++ b/tests/tail-2/pipe-f
@@ -0,0 +1,32 @@
+#!/bin/sh
+# ensure that :|tail -f doesn't hang, per POSIX
+
+# Copyright (C) 2009 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/>.
+
+if test "$VERBOSE" = yes; then
+ set -x
+ tail --version
+fi
+
+. $srcdir/test-lib.sh
+
+fail=0
+echo foo | timeout 2 tail -f -c3 > out || fail=1
+echo oo > exp || fail=1
+
+compare out exp || fail=1
+
+Exit $fail
diff --git a/tests/tail-2/pipe-f2 b/tests/tail-2/pipe-f2
new file mode 100755
index 000000000..406ebcc91
--- /dev/null
+++ b/tests/tail-2/pipe-f2
@@ -0,0 +1,37 @@
+#!/bin/sh
+# Ensure that "tail -f fifo" tails indefinitely.
+
+# Copyright (C) 2009 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+if test "$VERBOSE" = yes; then
+ set -x
+ tail --version
+fi
+
+. $srcdir/test-lib.sh
+
+mkfifo_or_skip_ fifo
+
+echo 1 > fifo &
+echo 1 > exp || framework_failure
+
+fail=0
+timeout 1 tail -f fifo > out
+test $? = 124 || fail=1
+
+compare out exp || fail=1
+
+Exit $fail