linux pid文件

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_IROTH
int 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);

: @myairen1365:哈哈，转眼间，这个我都写了三个年头了。换了两个镇江公司。从事了一个行业。

: @czc1009:呵呵，wireshark其实是能解rtmp的，端口1935，过滤为rtmpt就可以...

: 包解析部分清楚明白，要是能贴出wireshark的图就更好了，不过解析第14行错了吧，应该还是cli...

: @wei_bub:暂时公司没有考虑开源，产品还在研发中，估计以后稳定了把rtmp解析的库开源是有可能...

: 博主写的不错，挺清晰的，想问一下现在这套c++的是开源的么？我现在正在研究这方面的东西