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