mandhor · April 7, 2017 13:55 · Apr 7, 2017
diff --git a/lockrun.c b/lockrun.c
@@ -0,0 +1,411 @@
+/*
+ * $Id: //websites/unixwiz/unixwiz.net/webroot/tools/lockrun.c#8 $
+ *
+ * written by :	Stephen J. Friedl
+ *              Software Consultant
+ *		Southern California USA
+ *              [email protected]
+ *		http://www.unixwiz.net/tools/
+ *
+ *	===================================================================
+ *	======== This software is in the public domain, and can be ========
+ *	======== used by anybody for any purpose                   ========
+ *	===================================================================
+ *
+ *	Lockrun: This program is used to launch a program out with a lockout
+ *	so that only one can run at a time. It's mainly intended for use out
+ *	of cron so that our five-minute running jobs which run long don't get
+ *	walked on. We find this a *lot* with Cacti jobs which just get hung
+ *	up: it's better to miss a polling period than to stack them up and
+ *	slow each other down.
+ *
+ *	So we use a file which is used for locking: this program attempts to
+ *	lock the file, and if the lock exists, we have to either exit with
+ *	an error, or wait for it to release.
+ *
+ *		lockrun --lockfile=FILE -- my command here
+ *
+ * COMMAND LINE
+ * ------------
+ *
+ * --lockfile=F
+ *
+ *	Specify the name of a file which is used for locking. The file is
+ *	created if necessary (with mode 0666), and no I/O of any kind is
+ *	done. The file is never removed.
+ *
+ * --maxtime=N
+ *
+ *	The script being controlled should run for no more than <N> seconds,
+ *	and if it's beyond that time, we should report it to the standard
+ *	error (which probably gets routed to the user via cron's email).
+ *
+ * --wait
+ *
+ *	When a lock is hit, we normally exit with error, but --wait causes
+ *	it to loop until the lock is released.
+ *
+ * --sleep=N
+ * 
+ *	When using --wait, will sleep <N> seconds between attempts to acquire
+ *	the lock.
+ *
+ * --retries=N
+ *
+ *	When using --wait, will try only <N> attempts of acquiring the lock.
+ * 
+ * --verbose
+ *
+ *	Show a bit more runtime debugging.
+ *
+ * --quiet
+ *
+ *	Don't show "run is locked" error if things are busy; keeps cron from
+ *	overwhelming you with messages if lockrun overlap is not uncommon.
+ *
+ * --
+ *
+ *	Mark the end of the options: the command to run follows.
+ *	
+ *
+ * VERSION HISTORY
+ *
+ * 1.1.3 2014/11/03; now handle exit status correctly (thanks to Richard Faasen)
+ * 1.1.2 2013/04/26; now we use lockf() if the platform supports it
+ * 1.1.1 2012/09/05; added setsid() to make the controlled process a process
+ *			group leader
+ * 1.1.0 2012/09/05; added --version and --help; added --retries (thanks Dov Murik)
+ * 1.0.3 2010/11/20; added --quiet parameter
+ * 1.0.2 2009/06/25; added lockf() support for Solaris 10 (thanks Michal Bella)
+ * 1.0.1 2006/06/03; initial release	
+ * 
+ */
+
+#include <stdio.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/file.h>
+
+static const char Version[] = "lockrun 1.1.3 - 2014-11-03 - [email protected]";
+
+#ifndef __GNUC__
+# define __attribute__(x)	/* nothing */
+#endif
+
+
+#define STRMATCH(a,b)		(strcmp((a),(b)) == 0)
+
+#define UNUSED_PARAMETER(v)	((void)(v))
+
+#define	TRUE	1
+#define	FALSE	0
+
+static const char	*lockfile = 0;
+static int		wait_for_lock = FALSE;
+static mode_t		openmode = 0666;
+static int		sleeptime = 10;		/* seconds */
+static int		retries = 0;
+static int		Verbose = FALSE;
+static int		Maxtime  = 0;
+static int		Quiet = FALSE;
+
+static char *getarg(char *opt, char ***pargv);
+
+static void die(const char *format, ...)
+		__attribute__((noreturn))
+		__attribute__((format(printf, 1, 2)));
+
+#ifdef F_TLOCK
+# define WAIT_AND_LOCK(fd) lockf(fd, F_TLOCK,0)
+#else
+# define WAIT_AND_LOCK(fd) flock(fd, LOCK_EX | LOCK_NB)
+#endif
+
+static const char *const helptext[] = {
+	"Usage: lockrun [options] -- command args...",
+	"",
+	"  --help        Show this brief help listing",
+	"  --version     Report the version info",
+	"  --            Mark the end of lockrun options; command follows",
+	"  --verbose     Show a bit more runtime debugging",
+	"    -V",
+	"  --quiet       Exit quietly (and with success) if locked",
+	"    -q",
+	"  --lockfile=F  Specify lockfile as file <F>",
+	"    -L=F",
+	"  --wait        Wait for lockfile to appear (else exit on lock)",
+	"    -W",
+	"",
+	" Options with --wait:",
+	"",
+	"  --sleep=T     Sleep for <T> seconds on each wait loop",
+	"    -S=T",
+	"  --retries=N   Attempt <N> retries in each wait loop",
+	"    -R=N",
+	"  --maxtime=T   Wait for at most <T> seconds for a lock, then exit",
+	0,
+};
+
+static void show_help(const char *const *);
+
+int main(int argc, char **argv)
+{
+	char	*Argv0 = *argv;
+	int	rc;
+	int	lfd;
+	pid_t	childpid;
+	time_t	starttime;
+	int	attempts = 0;
+
+	UNUSED_PARAMETER(argc);
+
+	time(&starttime);
+
+	for ( argv++ ; *argv ; argv++ )
+	{
+		char    *arg = *argv;
+		char	*opt = strchr(arg, '=');
+
+		/* the -- token marks the end of the list */
+
+		if ( strcmp(*argv, "--") == 0 )
+		{
+			argv++;
+			break;
+		}
+
+		if (opt) *opt++ = '\0'; /* pick off the =VALUE part */
+
+		if ( STRMATCH(arg, "--version") )
+		{
+			puts(Version);
+			exit(EXIT_SUCCESS);
+		}
+
+		else if ( STRMATCH(arg, "--help"))
+		{
+			show_help(helptext);
+			exit(EXIT_SUCCESS);
+		}
+
+		else if ( STRMATCH(arg, "-L") || STRMATCH(arg, "--lockfile"))
+		{
+			lockfile = getarg(opt, &argv);
+		}
+
+		else if ( STRMATCH(arg, "-W") || STRMATCH(arg, "--wait"))
+		{
+			wait_for_lock = TRUE;
+		}
+
+		else if ( STRMATCH(arg, "-S") || STRMATCH(arg, "--sleep"))
+		{
+			sleeptime = atoi(getarg(opt, &argv));
+		}
+
+		else if ( STRMATCH(arg, "-R") || STRMATCH(arg, "--retries"))
+		{
+			retries = atoi(getarg(opt, &argv));
+		}
+
+		else if ( STRMATCH(arg, "-T") || STRMATCH(arg, "--maxtime"))
+		{
+			Maxtime = atoi(getarg(opt, &argv));
+		}
+
+		else if ( STRMATCH(arg, "-V") || STRMATCH(arg, "--verbose"))
+		{
+			Verbose++;
+		}
+
+		else if ( STRMATCH(arg, "-q") || STRMATCH(arg, "--quiet"))
+		{
+			Quiet = TRUE;
+		}
+
+		else
+		{
+			die("ERROR: \"%s\" is an invalid cmdline param", arg);
+		}
+	}
+
+	/*----------------------------------------------------------------
+	 * SANITY CHECKING
+	 *
+	 * Make sure that we have all the parameters we require
+	 */
+	if (*argv == 0)
+		die("ERROR: missing command to %s (must follow \"--\" marker) ", Argv0);
+
+	if (lockfile == 0)
+		die("ERROR: missing --lockfile=F parameter");
+
+	/*----------------------------------------------------------------
+	 * Open or create the lockfile, then try to acquire the lock. If
+	 * the lock is acquired immediately (==0), then we're done, but
+	 * if the lock is not available, we have to wait for it.
+	 *
+	 * We can either loop trying for the lock (for --wait), or exit
+	 * with error.
+	 */
+
+	if ( (lfd = open(lockfile, O_RDWR|O_CREAT, openmode)) < 0)
+		die("ERROR: cannot open(%s) [err=%s]", lockfile, strerror(errno));
+
+	while ( WAIT_AND_LOCK(lfd) != 0 )
+	{
+		attempts++;
+
+		if ( ! wait_for_lock )
+		{
+			if ( Quiet)
+				exit(EXIT_SUCCESS);
+			else
+				die("ERROR: cannot launch %s - run is locked", argv[0]);
+		}
+
+		if ( retries > 0 && attempts >= retries )
+		{
+			die("ERROR: cannot launch %s - run is locked (after %d attempts)", argv[0], attempts);
+		}
+
+		/* waiting */
+ 		if ( Verbose ) printf("(locked: sleeping %d secs, after attempt #%d)\n", sleeptime, attempts);
+
+		sleep(sleeptime);
+	}
+
+	fflush(stdout);
+
+	/* run the child */
+
+
+	if ( (childpid = fork()) == 0 )
+	{
+		/* IN THE CHILD */
+
+		close(lfd);		/* don't need the lock file */
+
+		/* Make ourselves a process group leader so that this and all
+		 * child processes can be sent a signal as a group. This may
+		 * be used someday to support a --kill option, though this is
+		 * is still tricky.
+		 *
+		 * PORTING NOTE: if "setsid" is undefined on your platform,
+		 * just comment it out and send me an email with info about
+		 * the build environment.
+		 */
+		(void) setsid();
+
+		execvp(argv[0], argv);
+	}
+	else if ( childpid > 0 )
+	{
+		/* IN THE PARENT */
+
+		time_t endtime;
+		pid_t  pid;
+		int exitstatus = 0;
+
+		if ( Verbose )
+		    printf("Waiting for process %ld\n", (long) childpid);
+
+		pid = waitpid(childpid, &exitstatus, 0);
+
+		time(&endtime);
+
+		endtime -= starttime;
+
+		if ( Verbose || (Maxtime > 0  &&  endtime > Maxtime) )
+		    printf("pid %d exited with status %d (time=%ld sec)\n", pid, exitstatus, endtime);
+
+		/* Reflect subprogram's exit status in lockrun's exit status */
+
+		if ( WIFEXITED(exitstatus) )
+		{
+			rc = WEXITSTATUS(exitstatus);
+		}
+		else
+		{
+			rc = 1;	/* SHOULD NEVER GET HERE */
+		}
+	}
+	else
+	{
+		die("ERROR: cannot fork [%s]", strerror(errno));
+	}
+
+	if ( Verbose ) printf("Exiting rc=%d\n", rc);
+
+	exit(rc);
+}
+
+
+/*! \fn static char *getarg(char *opt, char ***pargv)
+ *  \brief A function to parse calling parameters
+ *
+ *	This is a helper for the main arg-processing loop: we work with
+ *	options which are either of the form "-X=FOO" or "-X FOO"; we
+ *	want an easy way to handle either one.
+ *
+ *	The idea is that if the parameter has an = sign, we use the rest
+ *	of that same argv[X] string, otherwise we have to get the *next*
+ *	argv[X] string. But it's an error if an option-requiring param
+ *	is at the end of the list with no argument to follow.
+ *
+ *	The option name could be of the form "-C" or "--conf", but we
+ *	grab it from the existing argv[] so we can report it well.
+ *
+ * \return character pointer to the argument
+ *
+ */
+static char *getarg(char *opt, char ***pargv)
+{
+	const char *const optname = **pargv;
+
+	/* option already set? */
+	if (opt) return opt;
+
+	/* advance to next argv[] and try that one */
+	if ((opt = *++(*pargv)) == 0)
+		die("ERROR: option %s requires a parameter", optname);
+
+	return opt;
+}
+
+/*
+ * die()
+ *
+ *	Given a printf-style argument list, format it to the standard error,
+ *	append a newline, then exit with error status.
+ */
+
+static void die(const char *format, ...)
+{
+va_list	args;
+
+	va_start(args, format);
+	vfprintf(stderr, format, args);
+	putc('\n', stderr);
+	va_end(args);
+
+	exit(EXIT_FAILURE);
+}
+
+static void show_help(const char * const *p)
+{
+	puts(Version);
+	puts("");
+
+	for ( ; *p; p++ )
+	{
+		puts(*p);
+	}
+}