1 /*
2 pidfile.c - interact with pidfiles
3 Copyright (c) 1995 Martin Schulze <Martin.Schulze@Linux.DE>
4
5 This file is part of the sysklogd package, a kernel and system log daemon.
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License along
18 with this program; if not, write to the Free Software Foundation, Inc.,
19 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
20 */
21
22 /* left unaltered for tinc -- Ivo Timmermans */
23 /*
24 * Sat Aug 19 13:24:33 MET DST 1995: Martin Schulze
25 * First version (v0.2) released
26 */
27
28 #include "system.h"
29
30 #include "pidfile.h"
31
32 #ifndef HAVE_MINGW
33 /* read_pid
34 *
35 * Reads the specified pidfile and returns the read pid.
36 * 0 is returned if either there's no pidfile, it's empty
37 * or no pid can be read.
38 */
read_pid(const char * pidfile)39 pid_t read_pid(const char *pidfile) {
40 FILE *f;
41 long pid;
42
43 if(!(f = fopen(pidfile, "r"))) {
44 return 0;
45 }
46
47 if(fscanf(f, "%20ld", &pid) != 1) {
48 pid = 0;
49 }
50
51 fclose(f);
52 return (pid_t)pid;
53 }
54
55 /* check_pid
56 *
57 * Reads the pid using read_pid and looks up the pid in the process
58 * table (using /proc) to determine if the process already exists. If
59 * so the pid is returned, otherwise 0.
60 */
check_pid(const char * pidfile)61 pid_t check_pid(const char *pidfile) {
62 pid_t pid = read_pid(pidfile);
63
64 /* Amazing ! _I_ am already holding the pid file... */
65 if((!pid) || (pid == getpid())) {
66 return 0;
67 }
68
69 /*
70 * The 'standard' method of doing this is to try and do a 'fake' kill
71 * of the process. If an ESRCH error is returned the process cannot
72 * be found -- GW
73 */
74 /* But... errno is usually changed only on error.. */
75 errno = 0;
76
77 if(kill(pid, 0) && errno == ESRCH) {
78 return 0;
79 }
80
81 return pid;
82 }
83
84 /* write_pid
85 *
86 * Writes the pid to the specified file. If that fails 0 is
87 * returned, otherwise the pid.
88 */
write_pid(const char * pidfile)89 pid_t write_pid(const char *pidfile) {
90 FILE *f;
91 int fd;
92 pid_t pid;
93
94 if((fd = open(pidfile, O_RDWR | O_CREAT, 0644)) == -1) {
95 return 0;
96 }
97
98 if((f = fdopen(fd, "r+")) == NULL) {
99 close(fd);
100 return 0;
101 }
102
103 #ifdef HAVE_FLOCK
104
105 if(flock(fd, LOCK_EX | LOCK_NB) == -1) {
106 fclose(f);
107 return 0;
108 }
109
110 #endif
111
112 pid = getpid();
113
114 if(!fprintf(f, "%ld\n", (long)pid)) {
115 fclose(f);
116 return 0;
117 }
118
119 fflush(f);
120
121 #ifdef HAVE_FLOCK
122
123 if(flock(fd, LOCK_UN) == -1) {
124 fclose(f);
125 return 0;
126 }
127
128 #endif
129 fclose(f);
130
131 return pid;
132 }
133
134 /* remove_pid
135 *
136 * Remove the the specified file. The result from unlink(2)
137 * is returned
138 */
remove_pid(const char * pidfile)139 int remove_pid(const char *pidfile) {
140 return unlink(pidfile);
141 }
142 #endif
143