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1 | /* $Id: liblock.h,v 1.6 2009/06/27 16:32:38 mrsam Exp $ */ |
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2 | |
3 | #ifndef liblock_h |
4 | #define liblock_h |
5 | |
6 | /* |
7 | ** Copyright 1998 - 1999 Double Precision, Inc. See COPYING for |
8 | ** distribution information. |
9 | */ |
10 | |
11 | #ifdef __cplusplus |
12 | extern "C" { |
13 | #endif |
14 | |
15 | #include <sys/types.h> |
16 | |
17 | #ifndef liblock_config_h |
18 | #if HAVE_CONFIG_H |
19 | #include "config.h" |
20 | #endif |
21 | #endif |
22 | |
23 | #define ll_whence_start 0 |
24 | #define ll_whence_curpos 1 |
25 | #define ll_whence_end 2 |
26 | |
27 | #define ll_readlock 0 |
28 | #define ll_writelock 4 |
29 | #define ll_unlock 8 |
30 | #define ll_wait 16 |
31 | |
32 | int ll_lockfd(int, /* File descriptor */ |
33 | int, /* ll_ bitmask */ |
34 | LL_OFFSET_TYPE, /* Start */ |
35 | LL_OFFSET_TYPE); /* Length */ |
36 | |
37 | |
38 | /* Some useful macros: ll_lock_ex - exclusive lock on a file, |
39 | ll_lock_ex_test - attempt an exclusive lock on a file |
40 | ll_unlock_ex - unlock a file |
41 | */ |
42 | |
43 | #define ll_lock_ex(f) \ |
44 | ll_lockfd( (f), ll_writelock|ll_whence_start|ll_wait, 0, 0) |
45 | |
46 | #define ll_lock_ex_test(f) \ |
47 | ll_lockfd( (f), ll_writelock|ll_whence_start, 0, 0) |
48 | |
49 | #define ll_unlock_ex(f) \ |
50 | ll_lockfd( (f), ll_unlock|ll_whence_start, 0, 0) |
51 | |
52 | |
53 | /* |
54 | ** Value-added: functions that reliably start and stop a daemon process, |
55 | ** permitting only one daemon process running. Utilizes a lock file, and a |
56 | ** pidfile. |
57 | */ |
58 | |
59 | int ll_daemon_start(const char *lockfile); |
60 | void ll_daemon_started(const char *pidfile, int fd); |
61 | int ll_daemon_resetio(); |
62 | int ll_daemon_stop(const char *lockfile, const char *pidfile); |
63 | int ll_daemon_restart(const char *lockfile, const char *pidfile); |
64 | |
65 | /* |
66 | The basic scenario |
67 | |
68 | main() |
69 | { |
70 | if ((fd=ll_daemon_start(lockfilename)) < 0) |
71 | { |
72 | error(); exit(1); |
73 | } |
74 | |
75 | ... Some custom initialization here ... |
76 | |
77 | ll_daemon_started(pidfile, fd); |
78 | |
79 | ll_daemon_resetio(); ... this one is optional |
80 | } |
81 | |
82 | To stop this daemon: |
83 | |
84 | ll_daemon_stop (lockfilename, pidfile) |
85 | |
86 | |
87 | ll_daemon_start attempts to start a daemon process going. It does only |
88 | a partial setup. If it detects that the daemon process is already |
89 | running, it itself does an exit(0), not returning to the parent. |
90 | |
91 | If there was a failure starting a daemon process, -1 is return, else |
92 | we return a transparent file descriptor, which will have to be passed as |
93 | the secodn argument to ll_daemon_started(). |
94 | |
95 | When ll_daemon_start returns, we're already running in a partially set-up |
96 | daemon process. The setup isn't complete just yet. The parent function |
97 | can perform any other custom initialization. If initialization fails, |
98 | the parent function can simply exit. Otherwise, if the initialization |
99 | completes, ll_daemon_started must be called in order to save this daemon |
100 | process's pid in the pid file (2nd arg must be the return from ll_daemon_start. |
101 | |
102 | To stop a daemon process, simply call ll_daemon_stop. Nothing too |
103 | sophisticated here. |
104 | |
105 | To send the daemon process a SIGHUP, call ll_daemon_restart. |
106 | */ |
107 | |
108 | #ifdef __cplusplus |
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109 | } |
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110 | #endif |
111 | |
112 | #endif |