Linux进程单例模式运行

Linux进程单例模式运行

#include <iostream>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


int write_pid(const char* pidFile)
{
    char str[32] = {0};
    int fd = open(pidFile,O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);

    if(fd < 0)
    {   
        printf("can't open pidFile %s.\n",pidFile);
        exit(1);
    }   

    //Lock pidFile.
    if(lockf(fd, F_TLOCK,0))
         printf("can't lock pidFile %s.\n",pidFile);
        exit(0);
    }   

    sprintf(str,"%d\n",getpid());
    //Write pid ot pidFile
    ssize_t len = strlen(str);
    
    if(write(fd,str,len) != len)
    {   
        printf("can't write pid %s.\n",pidFile);
        exit(0);
    }   

    printf("write pid file %s.\n",pidFile);
    
    return fd; 
}

int main()
{

    int pid_fd = write_pid("server.pid");
    while(1)
    {   
        ;
    }

    lockf(pid_fd, F_ULOCK,0);
    close(pid_fd);
}

终端1

[banting@localhost test]$ ls -tlr
-rw-rw-r--. 1 banting banting      834 Jun 30 15:53 test75.cpp
-rwxrwxr-x. 1 banting banting    19760 Jun 30 16:03 test75
[banting@localhost test]$ g++ -g test75.cpp -o test75
[banting@localhost test]$
[banting@localhost test]$ ./test75
write pid file server.pid.

终端2

[banting@localhost test]$ ps -ef |grep test75
banting   519636  596192 99 16:03 pts/38   00:00:38 ./test75
banting   519676  518705  0 16:04 pts/96   00:00:00 grep --color=auto test75
[banting@localhost test]$ cat server.pid 
519636
[banting@localhost test]$ ./test75
can't lock pidFile server.pid.
[banting@localhost test]$