linux简单进程调用

父进程调用子进程，可以用的命令date，who，pwd，ls，等无参数的

#include <stdio.h>
#include <sys/wait.h>
#include <string.h>

#define MAXLINE 20

int main(void)
{
    char    buf[MAXLINE];    /* from apue.h */
    pid_t    pid;
    int        status;

    printf("%% ");    /* print prompt (printf requires %% to print %) */
    while (fgets(buf, MAXLINE, stdin) != NULL) {
        if (buf[strlen(buf) - 1] == '\n')
            buf[strlen(buf) - 1] = 0; /* replace newline with null */

        if ((pid = fork()) < 0) {
            puts("fork error");
        } else if (pid == 0) {        /* child */
            printf("pid:%d\n", pid);

            execlp(buf, buf, (char *)0);
            printf("couldn't execute: %s\n", buf);
            exit(127);
        }

        /* parent */
        if ((pid = waitpid(pid, &status, 0)) < 0)
        {
            printf("waitpid error !status:%d\n", status);
        }
        printf("%% ");
    }
    exit(0);
}