1 /* $NetBSD: pidfile.c,v 1.2 2025/02/11 17:48:30 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 #ifdef HAVE_CONFIG_H
32 #include "config.h"
33 #endif
34
35 #ifdef HAVE_SYS_CDEFS_H
36 #include <sys/cdefs.h>
37 #endif
38 #if defined(LIBC_SCCS) && !defined(lint)
39 __RCSID("$NetBSD: pidfile.c,v 1.2 2025/02/11 17:48:30 christos Exp $");
40 #endif
41
42 #include <sys/param.h>
43
44 #include <paths.h>
45 #include <stdbool.h>
46 #include <stdlib.h>
47 #include <stdio.h>
48 #include <string.h>
49 #include <unistd.h>
50 #ifdef HAVE_LIBUTIL_H
51 #include <libutil.h>
52 #endif
53 #ifdef HAVE_UTIL_H
54 #include <util.h>
55 #endif
56
57 static pid_t pidfile_pid;
58 static char *pidfile_path;
59
60 /* Deletes an existent pidfile iff it was created by this process. */
61 static void
pidfile_cleanup(void)62 pidfile_cleanup(void)
63 {
64
65 if ((pidfile_path != NULL) && (pidfile_pid == getpid()))
66 (void) unlink(pidfile_path);
67 }
68
69 /* Registers an atexit(3) handler to delete the pidfile we have generated.
70 * We only register the handler when we create a pidfile, so we can assume
71 * that the pidfile exists.
72 *
73 * Returns 0 on success or -1 if the handler could not be registered. */
74 static int
register_atexit_handler(void)75 register_atexit_handler(void)
76 {
77 static bool done = false;
78
79 if (!done) {
80 if (atexit(pidfile_cleanup) < 0)
81 return -1;
82 done = true;
83 }
84
85 return 0;
86 }
87
88 /* Given a new pidfile name in 'path', deletes any previously-created pidfile
89 * if the previous file differs to the new one.
90 *
91 * If a previous file is deleted, returns 1, which means that a new pidfile
92 * must be created. Otherwise, this returns 0, which means that the existing
93 * file does not need to be touched. */
94 static int
cleanup_old_pidfile(const char * path)95 cleanup_old_pidfile(const char* path)
96 {
97 if (pidfile_path != NULL) {
98 if (strcmp(pidfile_path, path) != 0) {
99 pidfile_cleanup();
100
101 free(pidfile_path);
102 pidfile_path = NULL;
103
104 return 1;
105 } else
106 return 0;
107 } else
108 return 1;
109 }
110
111 /* Constructs a name for a pidfile in the default location (/var/run). If
112 * 'basename' is NULL, uses the name of the current program for the name of
113 * the pidfile.
114 *
115 * Returns a pointer to a dynamically-allocatd string containing the absolute
116 * path to the pidfile; NULL on failure. */
117 static char *
generate_varrun_path(const char * bname)118 generate_varrun_path(const char *bname)
119 {
120 char *path;
121
122 if (bname == NULL)
123 bname = getprogname();
124
125 /* _PATH_VARRUN includes trailing / */
126 if (asprintf(&path, "%s%s.pid", _PATH_VARRUN, bname) == -1)
127 return NULL;
128 return path;
129 }
130
131 /* Creates a pidfile with the provided name. The new pidfile is "registered"
132 * in the global variables pidfile_path and pidfile_pid so that any further
133 * call to pidfile(3) can check if we are recreating the same file or a new
134 * one.
135 *
136 * Returns 0 on success or -1 if there is any error. */
137 static int
create_pidfile(const char * path)138 create_pidfile(const char* path)
139 {
140 FILE *f;
141
142 if (register_atexit_handler() == -1)
143 return -1;
144
145 if (cleanup_old_pidfile(path) == 0)
146 return 0;
147
148 pidfile_path = strdup(path);
149 if (pidfile_path == NULL)
150 return -1;
151
152 if ((f = fopen(path, "w")) == NULL) {
153 free(pidfile_path);
154 pidfile_path = NULL;
155 return -1;
156 }
157
158 pidfile_pid = getpid();
159
160 (void) fprintf(f, "%d\n", pidfile_pid);
161 (void) fclose(f);
162
163 return 0;
164 }
165
166 int
pidfile(const char * path)167 pidfile(const char *path)
168 {
169
170 if (path == NULL || strchr(path, '/') == NULL) {
171 char *default_path;
172
173 if ((default_path = generate_varrun_path(path)) == NULL)
174 return -1;
175
176 if (create_pidfile(default_path) == -1) {
177 free(default_path);
178 return -1;
179 }
180
181 free(default_path);
182 return 0;
183 } else
184 return create_pidfile(path);
185 }
186