Initial import of the lockf utility. It executes an arbitrary command

while holding an exclusive lock on a file.

3 files changed, 314 insertions, 0 deletions

diff --git a/usr.bin/lockf/Makefile b/usr.bin/lockf/Makefile
new file mode 100644
index 0000000..47fb6ab
--- /dev/null
+++ b/usr.bin/lockf/Makefile
@@ -0,0 +1,6 @@
+# $Id$
+
+PROG=	lockf
+CFLAGS+=-Wall
+
+.include <bsd.prog.mk>
diff --git a/usr.bin/lockf/lockf.1 b/usr.bin/lockf/lockf.1
new file mode 100644
index 0000000..6b78644
--- /dev/null
+++ b/usr.bin/lockf/lockf.1
@@ -0,0 +1,95 @@
+.\"
+.\" Copyright (C) 1997 John D. Polstra.  All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY JOHN D. POLSTRA AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL JOHN D. POLSTRA OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $Id$
+.\"
+.Dd January 8, 1997
+.Os FreeBSD
+.Dt LOCKF 1
+.Sh NAME
+.Nm lockf
+.Nd execute a command while holding a file lock
+.Sh SYNOPSIS
+.Nm
+.Op Fl s
+.Op Fl t Ar seconds
+.Ar file
+.Ar command
+.Op Ar arguments
+.Sh DESCRIPTION
+The
+.Nm
+utility acquires an exclusive lock on a
+.Ar file ,
+creating it if necessary.
+While holding the lock, it executes a
+.Ar command
+with optional
+.Ar arguments .
+After the
+.Ar command
+completes,
+.Nm
+releases the lock and removes the
+.Ar file .
+BSD-style locking is used, as described in
+.Xr flock 2 ;
+the mere existence of the 
+.Ar file
+is not considered to constitute a lock.
+.Pp
+The following options are supported:
+.Bl -tag -width Fl
+.It Fl s
+Causes
+.Nm
+to operate silently.
+Failure to acquire the lock is indicated only in the exit status.
+.It Fl t Ar seconds
+Specifies a timeout for waiting for the lock.  By default,
+.Nm
+waits indefinitely to acquire the lock.
+If a timeout is specified with this option,
+.Nm
+will wait at most the given number of
+.Ar seconds
+before giving up.  A timeout of 0 may be given, in which case
+.Nm
+will fail unless it can acquire the lock immediately.
+.El
+.Pp
+In no event will
+.Nm
+break a lock that is held by another process.
+.Sh DIAGNOSTICS
+If
+.Nm
+is unable to acquire the lock, it returns an exit status of 1.
+Otherwise, it returns the exit status produced by
+.Ar command .
+.Sh SEE ALSO
+.Xr flock 2 .
+.Sh AUTHORS
+John Polstra,
+.Aq jdp@polstra.com .
diff --git a/usr.bin/lockf/lockf.c b/usr.bin/lockf/lockf.c
new file mode 100644
index 0000000..319dc6b
--- /dev/null
+++ b/usr.bin/lockf/lockf.c
@@ -0,0 +1,213 @@
+/*
+ * Copyright (C) 1997 John D. Polstra.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY JOHN D. POLSTRA AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL JOHN D. POLSTRA OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $Id$
+ */
+
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static int acquire_lock(const char *name);
+static void cleanup(void);
+static void killed(int sig);
+static void timeout(int sig);
+static void usage(void);
+static void wait_for_lock(const char *name);
+
+static const char *lockname;
+static volatile sig_atomic_t timed_out;
+
+/*
+ * Execute an arbitrary command while holding a file lock.
+ */
+int
+main(int argc, char **argv)
+{
+    int ch;
+    int lockfd;
+    int silent;
+    int status;
+    int waitsec;
+    pid_t child;
+
+    silent = 0;
+    waitsec = -1;	/* Infinite. */
+    while ((ch = getopt(argc, argv, "st:")) != EOF) {
+	switch (ch) {
+
+	case 's':
+	    silent = 1;
+	    break;
+
+	case 't':
+	    {
+		char *endptr;
+		waitsec = strtol(optarg, &endptr, 0);
+		if (*optarg == '\0' || *endptr != '\0' || waitsec < 0)
+		    errx(1, "invalid timeout \"%s\"", optarg);
+	    }
+	    break;
+
+	default:
+	    usage();
+	}
+    }
+    if (argc - optind < 2)
+	usage();
+    lockname = argv[optind++];
+    argc -= optind;
+    argv += optind;
+
+    if (waitsec > 0) {		/* Set up a timeout. */
+	struct sigaction act;
+
+	act.sa_handler = timeout;
+	sigemptyset(&act.sa_mask);
+	act.sa_flags = 0;	/* Note that we do not set SA_RESTART. */
+
+	sigaction(SIGALRM, &act, NULL);
+	alarm(waitsec);
+    }
+
+    lockfd = acquire_lock(lockname);
+    while (lockfd == -1 && !timed_out && waitsec != 0) {
+	wait_for_lock(lockname);
+	lockfd = acquire_lock(lockname);
+    }
+
+    if (waitsec > 0)
+	alarm(0);
+
+    if (lockfd == -1) {		/* We failed to acquire the lock. */
+	if (silent)
+	    exit(1);
+	errx(1, "%s: already locked", lockname);
+    }
+
+    /* At this point, we own the lock. */
+
+    if (atexit(cleanup) == -1)
+	err(1, "atexit failed");
+
+    if ((child = fork()) == -1)
+	err(1, "cannot fork");
+
+    if (child == 0) {	/* The child process. */
+	close(lockfd);
+	execvp(argv[0], argv);
+	perror(argv[0]);
+	_exit(1);
+    }
+
+    /* This is the parent process. */
+
+    signal(SIGINT, SIG_IGN);
+    signal(SIGQUIT, SIG_IGN);
+    signal(SIGTERM, killed);
+
+    if (waitpid(child, &status, 0) == -1)
+	err(1, "waitpid failed");
+
+    return WIFEXITED(status) ? WEXITSTATUS(status) : 1;
+}
+
+/*
+ * Try to acquire a lock on the given file, but don't wait for it.  Returns
+ * an open file descriptor on success, or -1 on failure.
+ */
+static int
+acquire_lock(const char *name)
+{
+    int fd;
+
+    if ((fd = open(name, O_RDONLY|O_CREAT|O_EXLOCK|O_NONBLOCK, 0666)) == -1) {
+	if (errno == EAGAIN || errno == EINTR)
+	    return -1;
+	err(1, "cannot open %s", name);
+    }
+    return fd;
+}
+
+/*
+ * Remove the lock file.
+ */
+static void
+cleanup(void)
+{
+    if (unlink(lockname) == -1 && errno != ENOENT)
+	err(1, "cannot unlink %s", lockname);
+}
+
+/*
+ * Signal handler for SIGTERM.  Cleans up the lock file, then re-raises
+ * the signal.
+ */
+static void
+killed(int sig)
+{
+    cleanup();
+    signal(sig, SIG_DFL);
+    if (kill(getpid(), sig) == -1)
+	err(1, "kill failed");
+}
+
+/*
+ * Signal handler for SIGALRM.
+ */
+static void
+timeout(int sig)
+{
+    timed_out = 1;
+}
+
+static void
+usage(void)
+{
+    errx(1, "usage: lockf [-s] [-t seconds] file command [arguments]");
+}
+
+/*
+ * Wait until it might be possible to acquire a lock on the given file.
+ */
+static void
+wait_for_lock(const char *name)
+{
+    int fd;
+
+    if ((fd = open(name, O_RDONLY|O_EXLOCK)) == -1) {
+	if (errno == ENOENT || errno == EINTR)
+	    return;
+	err(1, "cannot open %s", name);
+    }
+    close(fd);
+    return;
+}