diff options
| -rw-r--r-- | sys-utils/flock.1 | 15 | ||||
| -rw-r--r-- | sys-utils/flock.c | 6 |
2 files changed, 16 insertions, 5 deletions
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] <file> -c <command> +[options] <file|directory> <command> [command args] .br .B flock -[options] <directory> -c <command> +[options] <file|directory> -c <command> .br .B flock [options] <file descriptor number> @@ -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 $FLOCKER is not set to the shell script that is being run, +then execute flock and grab an exclusive non-blocking lock (using the script +itself as the lock file) before re-execing itself with the right arguments. It +also sets the FLOCKER env var to the right value so it doesn't run again. .SH "EXIT STATUS" The command uses .B sysexits.h diff --git a/sys-utils/flock.c b/sys-utils/flock.c index b51415529..50435e0ec 100644 --- a/sys-utils/flock.c +++ b/sys-utils/flock.c @@ -48,9 +48,9 @@ static void __attribute__((__noreturn__)) usage(int ex) { fprintf(stderr, USAGE_HEADER); fprintf(stderr, - _(" %1$s [options] <file descriptor number>\n" - " %1$s [options] <file> -c <command>\n" - " %1$s [options] <directory> -c <command>\n"), + _(" %1$s [options] <file|directory> <command> [command args]\n" + " %1$s [options] <file|directory> -c <command>\n" + " %1$s [options] <file descriptor number>\n"), program_invocation_short_name); fputs(USAGE_OPTIONS, stderr); fputs(_( " -s --shared get a shared lock\n"), stderr); |