linux pid文件编程例子

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http://www.360doc.com/content/13/0919/20/13950301_315637950.shtml

linux使用pid file

UNIX环境编程里面，讲了如何使用pid文件，但是比较隐晦，今天整理一下：

原文如下：

#include stdio.h #include stdlib.h #include string.h #include unistd.h #include sys/types.h #include sys/stat.h #include errno.h #include fcntl.h #define PIDFILE deamon.pid #define write_lock(fd,offset,whence,len) lock_reg(fd,F_SETLK,F_WRLCK,offset,whence,len)int lock_reg(int fd, int cmd, int type, off_t offset, int whence, off_t len){ flock lock; lock.l_type = type; // F_RDLCK, F_WRLCK, F_UNLCK lock.l_start = offset; // type offset, relative to l_whence lock.l_whence = whence; // SEEK_SET, SEEK_CUR, SEEK_END lock.l_len = len; return (fcntl(fd, cmd, lock));// -rw-r--r-- // 644#define FILE_MODE S_IRUSR|S_IWUSR|S_IRGRP|S_IROTHint main(int argc, char** argv){ int fd; if((fd = open(PIDFILE, O_WRONLY | O_CREAT, FILE_MODE)) 0){ printf( open file error!  exit(errno); if(lock_reg(fd, 0, SEEK_SET, 0) 0){ if(errno == EACCES || errno == EAGAIN){ printf( deamon is already running!\n  exit(0); else{ printf( write lock error!\n  exit(errno); if(ftruncate(fd, 0) 0){ printf( trancate error!\n  exit(errno); char buf[11]; snprintf(buf, sizeof(buf), %d , getpid()); if(write(fd, buf, strlen(buf)) != strlen(buf)){ printf( write our pid error!\n  exit(errno); int val; if((val = fcntl(fd, F_GETFD, 0)) 0){ printf( fnctl F_GETFD error!\n  exit(errno); val |= FD_CLOEXEC; if(fcntl(fd, F_SETFD, val) 0){ printf( fcntl F_SETFD error!\n  exit(errno); sleep(3); printf( exit!  exit(0);

直接调用如下：

#include stdio.h #include stdlib.h #include string.h #include unistd.h #include sys/types.h #include sys/stat.h #include errno.h #include fcntl.h int main(int argc, char** argv){ int fd; // -rw-r--r--  // 644 int mode = S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH; const char* file_name = deamon.pid  // open pid file if((fd = open(file_name, O_WRONLY | O_CREAT, mode)) 0){ printf( open file error!  exit(errno); // require write lock flock lock; lock.l_type = F_WRLCK; // F_RDLCK, F_WRLCK, F_UNLCK lock.l_start = 0; // type offset, relative to l_whence lock.l_whence = SEEK_SET; // SEEK_SET, SEEK_CUR, SEEK_END lock.l_len = 0; if(fcntl(fd, F_SETLK, lock) 0){ if(errno == EACCES || errno == EAGAIN){ printf( deamon is already running!\n  exit(0); else{ printf( write lock error!\n  exit(errno); // truncate file if(ftruncate(fd, 0) 0){ printf( trancate error!\n  exit(errno); // write the pid char buf[11]; snprintf(buf, sizeof(buf), %d , getpid()); if(write(fd, buf, strlen(buf)) != strlen(buf)){ printf( write our pid error!\n  exit(errno); // auto close when fork child process. int val; if((val = fcntl(fd, F_GETFD, 0)) 0){ printf( fnctl F_GETFD error!\n  exit(errno); val |= FD_CLOEXEC; if(fcntl(fd, F_SETFD, val) 0){ printf( fcntl F_SETFD error!\n  exit(errno); sleep(3); printf( exit!  exit(0);