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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 <vapier@gentoo.org>
This commit is contained in:
Mike Frysinger 2012-12-26 15:10:29 -05:00 committed by Karel Zak
parent f5664477cb
commit 295dd90226
2 changed files with 16 additions and 5 deletions
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15
sys-utils/flock.1
View File

@ -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

6
sys-utils/flock.c
View File

@ -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);