一個Linux守候進程例子

其他程序可以調用void daemon_init(const char * cmd)方法，來初始化當前進程為守候進程

1. #include<stdio.h>
2. #include<unistd.h>
3. #include<sys/resource.h>
4. #include<fcntl.h>
5. #include<signal.h>
6. #include<syslog.h>
7. void daemon_init(const char * cmd);
8. int main(int argc, char * argv[])
9. {
10. daemon_init("liyachao_d");
11. time_t ticks;
12. while(1)
13. {
14. sleep(60);
15. ticks = time(NULL);
16. syslog(LOG_INFO,"%s",asctime(localtime(&ticks)));
17. }
18. return 0;
19. }
20. void daemon_init(const char * cmd)
21. {
22. int i;
23. int fd0;
24. int fd1;
25. int fd2;
26. pid_t pid;
27. struct rlimit rl;
28. struct sigaction sa;
29. /*清空文件默認生成權限*/
30. umask(0);
31. /*取得最大的文件描述符*/
32. if(getrlimit(RLIMIT_NOFILE,&rl) < 0 )
33. {
34. printf("can't get file limit.");
35. }
36. pid = fork();
37. if(pid < 0 )
38. {
39. printf("fork error.");
40. exit(1);
41. }
42. else if(pid > 0)
43. {
44. exit(0);
45. }
46. setsid();
47. /*
48. Ensure future opens won't allocate controlling TTYs.
50. */
51. sa.sa_handler =SIG_IGN;
52. sigemptyset(&sa.sa_mask);
53. sa.sa_flags = 0;
54. if(sigaction(SIGHUP,&sa,NULL) < 0 )
55. {
56. printf("catn't ignore SIGHUP");
57. exit(1);
58. }
60. pid = fork();
61. if(pid < 0 )
62. {
63. printf("child fork error.");
64. exit(1);
65. }
66. else if(pid > 0)
67. {
68. exit(0);
69. }
70. /*改變工作目錄到root*/
71. if(chdir("/") < 0 )
72. {
73. printf("can't change directory to /");
74. exit(1);
75. }
76. /*關閉所有的文件描述符*/
77. if (rl.rlim_max == RLIM_INFINITY)
78. {
79. rl.rlim_max = 1024;
80. }
81. for (i = 0; i < rl.rlim_max; i++)
82. {
83. close(i);
84. }
85. /*重定向文件描述符0，1，2，到/dev/null*/
86. fd0 = open("/dev/null",O_RDWR);
87. fd1 = open("/dev/null",O_RDONLY);
88. fd2 = open("/dev/null",O_RDWR);
89. openlog(cmd, LOG_CONS, LOG_DAEMON);
90. /*初始化日志文件*/
91. if (fd0 != 0 || fd1 != 1 || fd2 != 2)
92. {
93. syslog(LOG_ERR, "unexpected file descriptors %d %d %d",fd0, fd1, fd2);
94. exit(1);
96. }
97. }