From 295dd90226852a1f3b3dd108ed01dd1d7da92240 Mon Sep 17 00:00:00 2001 From: Mike Frysinger Date: Wed, 26 Dec 2012 15:10:29 -0500 Subject: flock: improve usage strings The current examples miss the best usage of all: specifying the command and its arguments directly on the command line. Add that to both the program usage and the man page. Signed-off-by: Mike Frysinger --- sys-utils/flock.1 | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) (limited to 'sys-utils/flock.1') diff --git a/sys-utils/flock.1 b/sys-utils/flock.1 index b50c619cf..b28526f69 100644 --- a/sys-utils/flock.1 +++ b/sys-utils/flock.1 @@ -29,10 +29,10 @@ flock \- manage locks from shell scripts .SH SYNOPSIS .B flock -[options] -c +[options] [command args] .br .B flock -[options] -c +[options] -c .br .B flock [options] @@ -120,6 +120,9 @@ shell2> flock -s -w .007 /tmp -c echo; /bin/echo $? Set shared lock to directory /tmp and the second command will not fail. Notice that attempting to get exclusive lock with second command would fail. .TP +shell> flock -x local-lock-file echo 'a b c' +Grab the exclusive lock "local-lock-file" before running echo with 'a b c'. +.TP ( .TQ flock -n 9 || exit 1 @@ -138,6 +141,14 @@ allows the lockfile to be created if it does not already exist, however, write permission is required. Using .I < requires that the file already exists but only read permission is required. +.TP +[ "${FLOCKER}" != "$0" ] && exec env FLOCKER="$0" flock -en "$0" "$0" "$@" || : +This is useful boilerplate code for shell scripts. Put it at the top of the +shell script you want to lock and it'll automatically lock itself on the first +run. If the env var $FLOCKER is not set to the shell script that is being run, +then execute flock and grab an exclusive non-blocking lock (using the script +itself as the lock file) before re-execing itself with the right arguments. It +also sets the FLOCKER env var to the right value so it doesn't run again. .SH "EXIT STATUS" The command uses .B sysexits.h -- cgit v1.2.3-55-g7522