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util-linux/sys-utils/flock.c

382 lines
9.8 KiB

/* Copyright 2003-2005 H. Peter Anvin - All Rights Reserved
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom
* the Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall
* be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <paths.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "c.h"
#include "nls.h"
#include "strutils.h"
#include "closestream.h"
#include "monotonic.h"
#include "timer.h"
static void __attribute__((__noreturn__)) usage(void)
{
fputs(USAGE_HEADER, stdout);
printf(
_(" %1$s [options] <file>|<directory> <command> [<argument>...]\n"
" %1$s [options] <file>|<directory> -c <command>\n"
" %1$s [options] <file descriptor number>\n"),
program_invocation_short_name);
fputs(USAGE_SEPARATOR, stdout);
fputs(_("Manage file locks from shell scripts.\n"), stdout);
fputs(USAGE_OPTIONS, stdout);
fputs(_( " -s, --shared get a shared lock\n"), stdout);
fputs(_( " -x, --exclusive get an exclusive lock (default)\n"), stdout);
fputs(_( " -u, --unlock remove a lock\n"), stdout);
fputs(_( " -n, --nonblock fail rather than wait\n"), stdout);
fputs(_( " -w, --timeout <secs> wait for a limited amount of time\n"), stdout);
fputs(_( " -E, --conflict-exit-code <number> exit code after conflict or timeout\n"), stdout);
fputs(_( " -o, --close close file descriptor before running command\n"), stdout);
fputs(_( " -c, --command <command> run a single command string through the shell\n"), stdout);
fputs(_( " -F, --no-fork execute command without forking\n"), stdout);
fputs(_( " --verbose increase verbosity\n"), stdout);
fputs(USAGE_SEPARATOR, stdout);
printf(USAGE_HELP_OPTIONS(26));
printf(USAGE_MAN_TAIL("flock(1)"));
exit(EXIT_SUCCESS);
}
static sig_atomic_t timeout_expired = 0;
static void timeout_handler(int sig __attribute__((__unused__)),
siginfo_t *info,
void *context __attribute__((__unused__)))
{
#ifdef HAVE_TIMER_CREATE
if (info->si_code == SI_TIMER)
#endif
timeout_expired = 1;
}
static int open_file(const char *filename, int *flags)
{
int fd;
int fl = *flags == 0 ? O_RDONLY : *flags;
errno = 0;
fl |= O_NOCTTY | O_CREAT;
fd = open(filename, fl, 0666);
/* Linux doesn't like O_CREAT on a directory, even though it
* should be a no-op; POSIX doesn't allow O_RDWR or O_WRONLY
*/
if (fd < 0 && errno == EISDIR) {
fl = O_RDONLY | O_NOCTTY;
fd = open(filename, fl);
}
if (fd < 0) {
warn(_("cannot open lock file %s"), filename);
if (errno == ENOMEM || errno == EMFILE || errno == ENFILE)
exit(EX_OSERR);
if (errno == EROFS || errno == ENOSPC)
exit(EX_CANTCREAT);
exit(EX_NOINPUT);
}
*flags = fl;
return fd;
}
static void __attribute__((__noreturn__)) run_program(char **cmd_argv)
{
execvp(cmd_argv[0], cmd_argv);
warn(_("failed to execute %s"), cmd_argv[0]);
_exit((errno == ENOMEM) ? EX_OSERR : EX_UNAVAILABLE);
}
int main(int argc, char *argv[])
{
struct ul_timer timer;
struct itimerval timeout;
int have_timeout = 0;
int type = LOCK_EX;
int block = 0;
int open_flags = 0;
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;
/*
* The default exit code for lock conflict or timeout
* is specified in man flock.1
*/
int conflict_exit_code = 1;
char **cmd_argv = NULL, *sh_c_argv[4];
const char *filename = NULL;
enum {
OPT_VERBOSE = CHAR_MAX + 1
};
static const struct option long_options[] = {
{"shared", no_argument, NULL, 's'},
{"exclusive", no_argument, NULL, 'x'},
{"unlock", no_argument, NULL, 'u'},
{"nonblocking", no_argument, NULL, 'n'},
{"nb", no_argument, NULL, 'n'},
{"timeout", required_argument, NULL, 'w'},
{"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'},
{NULL, 0, NULL, 0}
};
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
atexit(close_stdout);
strutils_set_exitcode(EX_USAGE);
if (argc < 2) {
warnx(_("not enough arguments"));
errtryhelp(EX_USAGE);
}
memset(&timeout, 0, sizeof timeout);
optopt = 0;
while ((opt =
getopt_long(argc, argv, "+sexnoFuw:E:hV?", long_options,
&ix)) != EOF) {
switch (opt) {
case 's':
type = LOCK_SH;
break;
case 'e':
case 'x':
type = LOCK_EX;
break;
case 'u':
type = LOCK_UN;
break;
case 'o':
do_close = 1;
break;
case 'F':
no_fork = 1;
break;
case 'n':
block = LOCK_NB;
break;
case 'w':
have_timeout = 1;
strtotimeval_or_err(optarg, &timeout.it_value,
_("invalid timeout value"));
break;
case 'E':
conflict_exit_code = strtos32_or_err(optarg,
_("invalid exit code"));
break;
case OPT_VERBOSE:
verbose = 1;
break;
case 'V':
printf(UTIL_LINUX_VERSION);
exit(EX_OK);
case 'h':
usage();
default:
errtryhelp(EX_USAGE);
}
}
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") ||
!strcmp(argv[optind + 1], "--command")) {
if (argc != optind + 3)
errx(EX_USAGE,
_("%s requires exactly one command argument"),
argv[optind + 1]);
cmd_argv = sh_c_argv;
cmd_argv[0] = getenv("SHELL");
if (!cmd_argv[0] || !*cmd_argv[0])
cmd_argv[0] = _PATH_BSHELL;
cmd_argv[1] = "-c";
cmd_argv[2] = argv[optind + 2];
cmd_argv[3] = NULL;
} else {
cmd_argv = &argv[optind + 1];
}
filename = argv[optind];
fd = open_file(filename, &open_flags);
} else if (optind < argc) {
/* Use provided file descriptor */
fd = strtos32_or_err(argv[optind], _("bad file descriptor"));
} else {
/* Bad options */
errx(EX_USAGE, _("requires file descriptor, file or directory"));
}
if (have_timeout) {
if (timeout.it_value.tv_sec == 0 &&
timeout.it_value.tv_usec == 0) {
/* -w 0 is equivalent to -n; this has to be
* special-cased because setting an itimer to zero
* means disabled!
*/
have_timeout = 0;
block = LOCK_NB;
} else
if (setup_timer(&timer, &timeout, &timeout_handler))
err(EX_OSERR, _("cannot set up timer"));
}
if (verbose)
gettime_monotonic(&time_start);
while (flock(fd, type | block)) {
switch (errno) {
case EWOULDBLOCK:
/* -n option set and failed to lock. */
if (verbose)
warnx(_("failed to get lock"));
exit(conflict_exit_code);
case EINTR:
/* Signal received */
if (timeout_expired) {
/* -w option set and failed to lock. */
if (verbose)
warnx(_("timeout while waiting to get lock"));
exit(conflict_exit_code);
}
/* otherwise try again */
continue;
case EIO:
case EBADF: /* since Linux 3.4 (commit 55725513) */
/* Probably NFSv4 where flock() is emulated by fcntl().
* Let's try to reopen in read-write mode.
*/
if (!(open_flags & O_RDWR) &&
type != LOCK_SH &&
filename &&
access(filename, R_OK | W_OK) == 0) {
close(fd);
open_flags = O_RDWR;
fd = open_file(filename, &open_flags);
if (open_flags & O_RDWR)
break;
}
/* fallthrough */
default:
/* Other errors */
if (filename)
warn("%s", filename);
else
warn("%d", fd);
exit((errno == ENOLCK
|| errno == ENOMEM) ? EX_OSERR : EX_DATAERR);
}
}
if (have_timeout)
cancel_timer(&timer);
if (verbose) {
struct timeval delta;
gettime_monotonic(&time_done);
timersub(&time_done, &time_start, &delta);
printf(_("%s: getting lock took %ld.%06ld seconds\n"),
program_invocation_short_name, delta.tv_sec,
delta.tv_usec);
}
status = EX_OK;
if (cmd_argv) {
pid_t w, f;
/* Clear any inherited settings */
signal(SIGCHLD, SIG_DFL);
if (verbose)
printf(_("%s: executing %s\n"), program_invocation_short_name, cmd_argv[0]);
if (!no_fork) {
f = fork();
if (f < 0)
err(EX_OSERR, _("fork failed"));
/* child */
else if (f == 0) {
if (do_close)
close(fd);
run_program(cmd_argv);
/* parent */
} else {
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;
}
} else
/* no-fork execution */
run_program(cmd_argv);
}
return status;
}