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 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 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 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 * 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 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 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