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pidfile.c revision 1.10 
      1 /*	$NetBSD: pidfile.c,v 1.10 2015/01/22 16:19:08 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1999 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe, Matthias Scheler and Julio Merino.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: pidfile.c,v 1.10 2015/01/22 16:19:08 christos Exp $");
     35 #endif
     36 
     37 #include <sys/param.h>
     38 
     39 #include <paths.h>
     40 #include <stdbool.h>
     41 #include <stdlib.h>
     42 #include <stdio.h>
     43 #include <string.h>
     44 #include <unistd.h>
     45 #include <util.h>
     46 
     47 static pid_t pidfile_pid;
     48 static char *pidfile_path;
     49 
     50 /* Deletes an existent pidfile iff it was created by this process. */
     51 static void
     52 pidfile_cleanup(void)
     53 {
     54 
     55 	if ((pidfile_path != NULL) && (pidfile_pid == getpid()))
     56 		(void) unlink(pidfile_path);
     57 }
     58 
     59 /* Registers an atexit(3) handler to delete the pidfile we have generated.
     60  * We only register the handler when we create a pidfile, so we can assume
     61  * that the pidfile exists.
     62  *
     63  * Returns 0 on success or -1 if the handler could not be registered. */
     64 static int
     65 register_atexit_handler(void)
     66 {
     67 	static bool done = false;
     68 
     69 	if (!done) {
     70 		if (atexit(pidfile_cleanup) < 0)
     71 			return -1;
     72 		done = true;
     73 	}
     74 
     75 	return 0;
     76 }
     77 
     78 /* Given a new pidfile name in 'path', deletes any previously-created pidfile
     79  * if the previous file differs to the new one.
     80  *
     81  * If a previous file is deleted, returns 1, which means that a new pidfile
     82  * must be created.  Otherwise, this returns 0, which means that the existing
     83  * file does not need to be touched. */
     84 static int
     85 cleanup_old_pidfile(const char* path)
     86 {
     87 	if (pidfile_path != NULL) {
     88 		if (strcmp(pidfile_path, path) != 0) {
     89 			pidfile_cleanup();
     90 
     91 			free(pidfile_path);
     92 			pidfile_path = NULL;
     93 
     94 			return 1;
     95 		} else
     96 			return 0;
     97 	} else
     98 		return 1;
     99 }
    100 
    101 /* Constructs a name for a pidfile in the default location (/var/run).  If
    102  * 'basename' is NULL, uses the name of the current program for the name of
    103  * the pidfile.
    104  *
    105  * Returns a pointer to a dynamically-allocatd string containing the absolute
    106  * path to the pidfile; NULL on failure. */
    107 static char *
    108 generate_varrun_path(const char *bname)
    109 {
    110 	char *path;
    111 
    112 	if (bname == NULL)
    113 		bname = getprogname();
    114 
    115 	/* _PATH_VARRUN includes trailing / */
    116 	if (asprintf(&path, "%s%s.pid", _PATH_VARRUN, basename) == -1)
    117 		return NULL;
    118 	return path;
    119 }
    120 
    121 /* Creates a pidfile with the provided name.  The new pidfile is "registered"
    122  * in the global variables pidfile_path and pidfile_pid so that any further
    123  * call to pidfile(3) can check if we are recreating the same file or a new
    124  * one.
    125  *
    126  * Returns 0 on success or -1 if there is any error. */
    127 static int
    128 create_pidfile(const char* path)
    129 {
    130 	FILE *f;
    131 
    132 	if (register_atexit_handler() == -1)
    133 		return -1;
    134 
    135 	if (cleanup_old_pidfile(path) == 0)
    136 		return 0;
    137 
    138 	pidfile_path = strdup(path);
    139 	if (pidfile_path == NULL)
    140 		return -1;
    141 
    142 	if ((f = fopen(path, "w")) == NULL) {
    143 		free(pidfile_path);
    144 		pidfile_path = NULL;
    145 		return -1;
    146 	}
    147 
    148 	pidfile_pid = getpid();
    149 
    150 	(void) fprintf(f, "%d\n", pidfile_pid);
    151 	(void) fclose(f);
    152 
    153 	return 0;
    154 }
    155 
    156 int
    157 pidfile(const char *path)
    158 {
    159 
    160 	if (path == NULL || strchr(path, '/') == NULL) {
    161 		char *default_path;
    162 
    163 		if ((default_path = generate_varrun_path(path)) == NULL)
    164 			return -1;
    165 
    166 		if (create_pidfile(default_path) == -1) {
    167 			free(default_path);
    168 			return -1;
    169 		}
    170 
    171 		free(default_path);
    172 		return 0;
    173 	} else
    174 		return create_pidfile(path);
    175 }
    176