tail: use inotify if it is available

* NEWS: Document the new feature.
* m4/jm-macros.m4: Check if inotify is present.
* src/tail.c (tail_forever_inotify): New function.
(main): Use the inotify-based function, if possible.
* tests/Makefile.am: Add new tests for tail.
* tests/test-lib.sh (require_proc_pid_status_, get_process_status_):
New functions.
* tests/tail-2/pid: New file.
* tests/tail-2/wait: New file.
* tests/tail-2/tail-n0f: Refactor code into the test-lib.sh
require_proc_pid_status_ function.

5 files changed, 219 insertions, 7 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index 2405ce44f..24f54baef 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -137,6 +137,7 @@ TESTS =						\
   misc/date-next-dow				\
   misc/ptx-overrun				\
   misc/xstrtol					\
+  tail-2/pid					\
   misc/od					\
   misc/mktemp					\
   misc/arch					\
@@ -243,6 +244,7 @@ TESTS =						\
   misc/unexpand					\
   misc/uniq					\
   misc/xattr					\
+  tail-2/wait					\
   chmod/c-option				\
   chmod/equal-x					\
   chmod/equals					\
diff --git a/tests/tail-2/pid b/tests/tail-2/pid
new file mode 100755
index 000000000..ff2f099ad
--- /dev/null
+++ b/tests/tail-2/pid
@@ -0,0 +1,68 @@
+#!/bin/sh
+# Test the --pid option of tail.
+
+# Copyright (C) 2003, 2006-2009 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
+
+. $srcdir/test-lib.sh
+
+require_proc_pid_status_
+
+touch here || framework_failure
+
+
+fail=0
+
+# Use tail itself to create a background process.
+
+tail -f here &
+bg_pid=$!
+
+tail -s0.1 -f here --pid=$bg_pid &
+
+pid=$!
+
+sleep 0.5
+
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) ;;
+    *) echo $0: process dead 1>&2; fail=1 ;;
+  esac
+  kill $pid
+fi
+
+kill $bg_pid
+
+sleep 0.5
+
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) echo $0: process still active 1>&2; fail=1 ;;
+    *) ;;
+  esac
+  kill $pid
+fi
+
+Exit $fail
diff --git a/tests/tail-2/tail-n0f b/tests/tail-2/tail-n0f
index bf19cf54c..322fddcf3 100755
--- a/tests/tail-2/tail-n0f
+++ b/tests/tail-2/tail-n0f
@@ -2,7 +2,7 @@
 # Make sure that `tail -n0 -f' and `tail -c0 -f' sleep
 # rather than doing what amounted to a busy-wait.
 
-# Copyright (C) 2003, 2006-2008 Free Software Foundation, Inc.
+# Copyright (C) 2003, 2006-2009 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
@@ -28,12 +28,7 @@ fi
 
 . $srcdir/test-lib.sh
 
-sleep 2 &
-pid=$!
-sleep .5
-grep '^State:[	 ]*[S]' /proc/$pid/status > /dev/null 2>&1 ||
-  skip_test_ "/proc/$pid/status: missing or 'different'"
-kill $pid
+require_proc_pid_status_
 
 touch empty || framework_failure
 echo anything > nonempty || framework_failure
diff --git a/tests/tail-2/wait b/tests/tail-2/wait
new file mode 100755
index 000000000..7eee8b159
--- /dev/null
+++ b/tests/tail-2/wait
@@ -0,0 +1,131 @@
+#!/bin/sh
+# Make sure that `tail -f' returns immediately if a file doesn't exist
+# while `tail -F' waits for it to appear.
+
+# Copyright (C) 2003, 2006-2009 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
+
+. $srcdir/test-lib.sh
+
+require_proc_pid_status_
+
+touch here || framework_failure
+touch k || framework_failure
+(touch not_accessible && chmod 0 not_accessible) || framework_failure
+
+fail=0
+
+tail -s0.1 -f not_here &
+pid=$!
+sleep .5
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) echo $0: process still active 1>&2; fail=1 ;;
+    *) ;;
+  esac
+  kill $pid
+fi
+
+tail -s0.1 -f not_accessible &
+pid=$!
+sleep .5
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) echo $0: process still active 1>&2; fail=1 ;;
+    *) ;;
+  esac
+  kill $pid
+fi
+
+(tail -s0.1 -f here 2>tail.err) &
+pid=$!
+sleep .5
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) ;;
+    *)  echo $0: process died 1>&2; fail=1 ;;
+  esac
+  kill $pid
+fi
+
+
+# `tail -F' must wait in any case.
+
+(tail -s0.1 -F here 2>>tail.err) &
+pid=$!
+sleep .5
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) ;;
+    *) echo $0: process died 1>&2; fail=1 ;;
+  esac
+  kill $pid
+fi
+
+tail -s0.1 -F not_accessible &
+pid=$!
+sleep .5
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) ;;
+    *) echo $0: process died 1>&2; fail=1 ;;
+  esac
+  kill $pid
+fi
+
+tail -s0.1 -F not_here &
+pid=$!
+sleep .5
+state=$(get_process_status_ $pid)
+
+if test -n "$state"; then
+  case $state in
+    S*) ;;
+    *) echo $0: process died 1>&2; fail=1 ;;
+  esac
+  kill $pid
+fi
+
+test -s tail.err && fail=1
+
+tail -s.1 -F k > tail.out &
+pid=$!
+sleep .5
+mv k l
+sleep .5
+touch k
+mv k l
+sleep .5
+echo NO >> l
+sleep .5
+kill $pid
+test -s tail.out && fail=1
+
+Exit $fail
diff --git a/tests/test-lib.sh b/tests/test-lib.sh
index e5eed8db6..d99e3a966 100644
--- a/tests/test-lib.sh
+++ b/tests/test-lib.sh
@@ -122,6 +122,11 @@ uid_is_privileged_()
   esac
 }
 
+get_process_status_()
+{
+  sed -n '/^State:[	 ]*\([[:alpha:]]\).*/s//\1/p' /proc/$1/status
+}
+
 # Convert an ls-style permission string, like drwxr----x and -rw-r-x-wx
 # to the equivalent chmod --mode (-m) argument, (=,u=rwx,g=r,o=x and
 # =,u=rw,g=rx,o=wx).  Ignore ACLs.
@@ -234,6 +239,17 @@ of group names or numbers.  E.g.,
   esac
 }
 
+# Is /proc/$PID/status supported?
+require_proc_pid_status_()
+{
+    sleep 2 &
+    local pid=$!
+    sleep .5
+    grep '^State:[	 ]*[S]' /proc/$pid/status > /dev/null 2>&1 ||
+    skip_test_ "/proc/$pid/status: missing or 'different'"
+    kill $pid
+}
+
 # Does the current (working-dir) file system support sparse files?
 require_sparse_support_()
 {