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flock: Introduce no-fork option. 

When guarding a command with flock it is sometimes preferable to not leave a
flock process waiting around for the command to exit.
This commit is contained in:
Terry Burton 2016-04-14 12:27:52 +01:00
parent 3e584e8576
commit 703251401c
2 changed files with 49 additions and 27 deletions
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8
sys-utils/flock.1
View File

@ -70,6 +70,14 @@ The exit code used when the \fB\-n\fP option is in use, and the
conflicting lock exists, or the \fB\-w\fP option is in use,
and the timeout is reached. The default value is \fB1\fR.
.TP
.BR \-F , " \-\-no\-fork"
Do not fork before executing
.IR command .
Upon execution the flock process is replaced by
.IR command
which continues to hold the lock. This option is incompatible with
\fB\-\-close\fR as there would otherwise be nothing left to hold the lock.
.TP
.BR \-e , " \-x" , " \-\-exclusive"
Obtain an exclusive lock, sometimes called a write lock. This is the
default.

68
sys-utils/flock.c
View File

@ -67,6 +67,7 @@ static void __attribute__((__noreturn__)) usage(int ex)
fputs(_( " -E, --conflict-exit-code <number> exit code after conflict or timeout\n"), stderr);
fputs(_( " -o, --close close file descriptor before running command\n"), stderr);
fputs(_( " -c, --command <command> run a single command string through the shell\n"), stderr);
fputs(_( " -F, --no-fork execute command without forking\n"), stderr);
fputs(_( " --verbose increase verbosity\n"), stderr);
fprintf(stderr, USAGE_SEPARATOR);
fprintf(stderr, USAGE_HELP);
@ -125,6 +126,7 @@ int main(int argc, char *argv[])
int fd = -1;
int opt, ix;
int do_close = 0;
int no_fork = 0;
int status;
int verbose = 0;
struct timeval time_start, time_done;
@ -148,6 +150,7 @@ int main(int argc, char *argv[])
{"wait", required_argument, NULL, 'w'},
{"conflict-exit-code", required_argument, NULL, 'E'},
{"close", no_argument, NULL, 'o'},
{"no-fork", no_argument, NULL, 'F'},
{"verbose", no_argument, NULL, OPT_VERBOSE},
{"help", no_argument, NULL, 'h'},
{"version", no_argument, NULL, 'V'},
@ -166,7 +169,7 @@ int main(int argc, char *argv[])
optopt = 0;
while ((opt =
getopt_long(argc, argv, "+sexnouw:E:hV?", long_options,
getopt_long(argc, argv, "+sexnoFuw:E:hV?", long_options,
&ix)) != EOF) {
switch (opt) {
case 's':
@ -182,6 +185,9 @@ int main(int argc, char *argv[])
case 'o':
do_close = 1;
break;
case 'F':
no_fork = 1;
break;
case 'n':
block = LOCK_NB;
break;
@ -209,6 +215,10 @@ int main(int argc, char *argv[])
}
}
if (no_fork && do_close)
errx(EX_USAGE,
_("the --no-fork and --close options are incompatible"));
if (argc > optind + 1) {
/* Run command */
if (!strcmp(argv[optind + 1], "-c") ||
@ -320,36 +330,40 @@ int main(int argc, char *argv[])
signal(SIGCHLD, SIG_DFL);
if (verbose)
printf(_("%s: executing %s\n"), program_invocation_short_name, cmd_argv[0]);
f = fork();
if (f < 0) {
err(EX_OSERR, _("fork failed"));
} else if (f == 0) {
if (do_close)
close(fd);
execvp(cmd_argv[0], cmd_argv);
/* execvp() failed */
warn(_("failed to execute %s"), cmd_argv[0]);
_exit((errno == ENOMEM) ? EX_OSERR : EX_UNAVAILABLE);
} else {
do {
w = waitpid(f, &status, 0);
if (w == -1 && errno != EINTR)
break;
} while (w != f);
if (!no_fork) {
f = fork();
if (f < 0) {
err(EX_OSERR, _("fork failed"));
if (f != 0) {
do {
w = waitpid(f, &status, 0);
if (w == -1 && errno != EINTR)
break;
} while (w != f);
if (w == -1) {
status = EXIT_FAILURE;
warn(_("waitpid failed"));
} else if (WIFEXITED(status))
status = WEXITSTATUS(status);
else if (WIFSIGNALED(status))
status = WTERMSIG(status) + 128;
else
/* WTF? */
status = EX_OSERR;
if (w == -1) {
status = EXIT_FAILURE;
warn(_("waitpid failed"));
} else if (WIFEXITED(status))
status = WEXITSTATUS(status);
else if (WIFSIGNALED(status))
status = WTERMSIG(status) + 128;
else
/* WTF? */
status = EX_OSERR;
}
goto out;
}
}
if (do_close)
close(fd);
execvp(cmd_argv[0], cmd_argv);
/* execvp() failed */
warn(_("failed to execute %s"), cmd_argv[0]);
_exit((errno == ENOMEM) ? EX_OSERR : EX_UNAVAILABLE);
}
out:
return status;
}