p10-6.c

SUN Solaris8平台下进程间通信

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include "err_exit.h"
#include "filelock.h"
void lockabyte(const char *, int , off_t);
int main(void)
{
    int fd;
    pid_t pid;
    /* 创建文件并写二个字节*/
    if ((fd = creat("templock", 0666)) < 0)
        err_exit("creat error");
    write(fd, "ab", 2) ;

    if((pid = fork()) < 0) 
        err_exit("fork error");
    if (pid == 0) {              /* 子进程 */
        lockabyte("child", fd, 1);
        sleep(10);               /* 留出时间以便父进程先锁住字节2 */
        lockabyte("child", fd, 2);
    } else {                      /* 父进程 */
        lockabyte("parent", fd, 2);
        sleep(10);                /* 留出时间以便子进程先锁住字节1 */
        lockabyte("parent", fd, 1);
    }
    exit(EXIT_SUCCESS);
}
static void lockabyte(const char *name, int fd, off_t offset)
{
    if (WRITEW_LOCK(fd, offset, SEEK_SET, 1) <0 ) {
        fprintf(stderr,"%s: ",name);
        err_exit("WRITEW_LOCK error");
    }
    printf("%s: got the lock,byte %d\n",name, offset);
}