1 /* $NetBSD: pidfile.c,v 1.11 2015/01/22 19:04:28 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 1.11 2015/01/22 19:04:28 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
pidfile_cleanup(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
register_atexit_handler(void)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
cleanup_old_pidfile(const char * path)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 * 'bname' 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 *
generate_varrun_path(const char * bname)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, bname) == -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
create_pidfile(const char * path)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
pidfile(const char * path)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