Mutually exclusive access to shared resources among multiple processes under Linux

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h    
> #include <sys/mman.h> #include <pthread.h> pthread_mutex_t* G_mutex;    
    Create a shared mutex void Init_mutex (void) {int ret; G_mutex must be shared between processes, you cannot achieve a mutex g_mutex= (pthread_mutex_t*) mmap (NULL, sizeof (pthread_mutex_t), prot_read| Prot_write, map_shared|    
    Map_anonymous,-1, 0);    
        if (Map_failed==g_mutex) {perror ("mmap");    
    Exit (1);    
    }//Set attr properties pthread_mutexattr_t attr;    
    Pthread_mutexattr_init (&ATTR); Be sure to set the pthread_process_shared//specific reference http://blog.chinaunix.net/u/22935/showart_340408.html Ret=pthread_m    
    Utexattr_setpshared (&attr,pthread_process_shared);    
        if (ret!=0) {perror ("Init_mutex pthread_mutexattr_setpshared");    
    Exit (1); } pthread_mUtex_init (G_mutex, &attr);    
    int main (int argc, char *argv[]) {Init_mutex ();        
    int ret;    
    Char str1[]= "This are child process/r/n";    
    Char str2[]= "This is Father process/r/n"; int Fd=open ("tmp", o_rdwr| O_creat|    
    O_trunc, 0666);    
        if ( -1==FD) {perror ("open");    
    Exit (1);    
    } pid_t pid;    
    Pid=fork ();    
        if (pid<0) {perror ("fork");    
    Exit (1);    
        else if (0==pid) {ret=pthread_mutex_lock (G_mutex);    
        if (ret!=0) {perror ("Child Pthread_mutex_lock");    
        Sleep (10);//Whether the test can prevent the parent process from writing write (FD, str1, sizeof (STR1));      
        Ret=pthread_mutex_unlock (G_mutex);    
        if (ret!=0) {perror ("Child Pthread_mutex_unlock");     
      } else {sleep (2);//Ensure that the child process executes first  Ret=pthread_mutex_lock (G_mutex);    
        if (ret!=0) {perror ("Father Pthread_mutex_lock");    
        Write (fd, str2, sizeof (STR2));      
        Ret=pthread_mutex_unlock (G_mutex);    
        if (ret!=0) {perror ("Father Pthread_mutex_unlock");    
    }} wait (NULL);    
Munmap (G_mutex, sizeof (pthread_mutex_t)); }

The contents of the after-run TMP file are:

This are child process

This is Father process