一个Linux守候进程例子

其他程序可以调用void daemon_init(const char * cmd)方法，来初始化当前进程为守候进程

 #include<stdio.h>#include<unistd.h>#include<sys/resource.h>#include<fcntl.h>#include<signal.h>#include<syslog.h>void daemon_init(const char * cmd);int main(int argc, char * argv[]){ daemon_init("liyachao_d"); time_t ticks; while(1) { sleep(60); ticks = time(NULL); syslog(LOG_INFO,"%s",asctime(localtime(&ticks))); } return 0;}void daemon_init(const char * cmd){ int i; int fd0; int fd1; int fd2; pid_t pid; struct rlimit rl; struct sigaction sa; /*清空文件默认生成权限*/ umask(0); /*取得最大的文件描述符*/ if(getrlimit(RLIMIT_NOFILE,&rl) < 0 ) { printf("can't get file limit."); } pid = fork(); if(pid < 0 ) { printf("fork error."); exit(1); } else if(pid > 0) { exit(0); } setsid(); /* Ensure future opens won't allocate controlling TTYs. */ sa.sa_handler =SIG_IGN; sigemptyset(&sa.sa_mask); sa.sa_flags = 0; if(sigaction(SIGHUP,&sa,NULL) < 0 ) { printf("catn't ignore SIGHUP"); exit(1); } pid = fork(); if(pid < 0 ) { printf("child fork error."); exit(1); } else if(pid > 0) { exit(0); } /*改变工作目录到root*/ if(chdir("/") < 0 ) { printf("can't change directory to /"); exit(1); } /*关闭所有的文件描述符*/ if (rl.rlim_max == RLIM_INFINITY) { rl.rlim_max = 1024; } for (i = 0; i < rl.rlim_max; i++) { close(i); } /*重定向文件描述符0，1，2，到/dev/null*/ fd0 = open("/dev/null",O_RDWR); fd1 = open("/dev/null",O_RDONLY); fd2 = open("/dev/null",O_RDWR); openlog(cmd, LOG_CONS, LOG_DAEMON); /*初始化日志文件*/ if (fd0 != 0 || fd1 != 1 || fd2 != 2) { syslog(LOG_ERR, "unexpected file descriptors %d %d %d",fd0, fd1, fd2); exit(1); }}