cw_pipe.c

提供进程间通过管道通信的例子

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#define MAXLINE 256

void err_sys (const char* info)
{
        perror (info);
        exit (1);
}

int main (void)
{
    int n, fd [2];
    pid_t pid;
    char line [MAXLINE];
    //char *argv[]={"ps","-l",NULL};
if (pipe (fd) < 0)
         err_sys ("pipe error");
    if ( (pid = fork ()) < 0)
         err_sys ("fork error");
    else if (pid > 0) { // parent
         //execvp(argv[0] ,&argv[0]);
         close (fd [0]);
         write (fd [1], "hello world\n", 12);
    }
    else {      // child
         printf("current process id is %d\n",getpid ());
         printf("parent process id is %d\n",getppid ());

        printf("uid is %d\n",getuid ());

        printf("gid is %d\n",getgid ());
        printf("user login id is %s\n",getlogin());
        //uid_t getegid (void);
        // execvp(argv[0] ,&argv[0]);
         close (fd [1]);
         n = read (fd[0], line, MAXLINE);
         write (STDOUT_FILENO, line, n);
        // execvp(argv[0] ,&argv[0]);
    }
    exit (0);
}