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Diffstat (limited to 'sys-utils/flock.c')
| -rw-r--r-- | sys-utils/flock.c | 343 |
1 files changed, 343 insertions, 0 deletions
diff --git a/sys-utils/flock.c b/sys-utils/flock.c new file mode 100644 index 0000000..5a3422a --- /dev/null +++ b/sys-utils/flock.c @@ -0,0 +1,343 @@ +/* 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" + +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"), + program_invocation_short_name); + fputs(USAGE_OPTIONS, stderr); + fputs(_( " -s --shared get a shared lock\n"), stderr); + fputs(_( " -x --exclusive get an exclusive lock (default)\n"), stderr); + fputs(_( " -u --unlock remove a lock\n"), stderr); + fputs(_( " -n --nonblock fail rather than wait\n"), stderr); + fputs(_( " -w --timeout <secs> wait for a limited amount of time\n"), stderr); + 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); + fprintf(stderr, USAGE_SEPARATOR); + fprintf(stderr, USAGE_HELP); + fprintf(stderr, USAGE_VERSION); + fprintf(stderr, USAGE_MAN_TAIL("flock(1)")); + exit(ex); +} + +static sig_atomic_t timeout_expired = 0; + +static void timeout_handler(int sig __attribute__((__unused__))) +{ + timeout_expired = 1; +} + +static void strtotimeval(const char *str, struct timeval *tv) +{ + double user_input; + + user_input = strtod_or_err(str, "bad number"); + tv->tv_sec = (time_t) user_input; + tv->tv_usec = (long)((user_input - tv->tv_sec) * 1000000); + if ((tv->tv_sec + tv->tv_usec) == 0) + errx(EX_USAGE, _("timeout cannot be zero")); +} + +static void setup_timer(struct itimerval *timer, struct itimerval *old_timer, + struct sigaction *sa, struct sigaction *old_sa) +{ + memset(sa, 0, sizeof *sa); + sa->sa_handler = timeout_handler; + sa->sa_flags = SA_RESETHAND; + sigaction(SIGALRM, sa, old_sa); + setitimer(ITIMER_REAL, timer, old_timer); +} + +static void cancel_timer(struct itimerval *old_timer, struct sigaction *old_sa) +{ + setitimer(ITIMER_REAL, old_timer, NULL); + sigaction(SIGALRM, old_sa, NULL); +} + +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; +} + +int main(int argc, char *argv[]) +{ + struct itimerval timeout, old_timer; + 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 status; + /* + * 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; + struct sigaction sa, old_sa; + + 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'}, + {"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); + + if (argc < 2) + usage(EX_USAGE); + + memset(&timeout, 0, sizeof timeout); + + optopt = 0; + while ((opt = + getopt_long(argc, argv, "+sexnouw: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 'n': + block = LOCK_NB; + break; + case 'w': + have_timeout = 1; + strtotimeval(optarg, &timeout.it_value); + break; + case 'E': + conflict_exit_code = strtos32_or_err(optarg, + _("invalid exit code")); + break; + case 'V': + printf("flock (%s)\n", PACKAGE_STRING); + exit(EX_OK); + default: + /* optopt will be set if this was an unrecognized + * option, i.e. *not* 'h' or '? + */ + usage(optopt ? EX_USAGE : 0); + break; + } + } + + 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] = 0; + } else { + cmd_argv = &argv[optind + 1]; + } + + filename = argv[optind]; + fd = open_file(filename, &open_flags); + + } else if (optind < argc) { + /* Use provided file descriptor */ + fd = (int)strtol_or_err(argv[optind], "bad number"); + } 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 + setup_timer(&timeout, &old_timer, &sa, &old_sa); + } + + while (flock(fd, type | block)) { + switch (errno) { + case EWOULDBLOCK: + /* -n option set and failed to lock. */ + exit(conflict_exit_code); + case EINTR: + /* Signal received */ + if (timeout_expired) + /* -w option set and failed to lock. */ + exit(conflict_exit_code); + /* otherwise try again */ + continue; + case EIO: + /* 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 && + 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; + } + /* go through */ + 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(&old_timer, &old_sa); + + status = EX_OK; + + if (cmd_argv) { + pid_t w, f; + /* Clear any inherited settings */ + signal(SIGCHLD, SIG_DFL); + 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("%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 (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; + } + } + + return status; +} |