#include "apue.h"
#include <sys/wait.h>

int main(int argc, cahr* argv[]) {
char buf[MAXLINE];
pid_t pid;
int status;

printf("%%");
while (fgets(buf, MAXLINE, stdin) != NULL) {
if (buf[strlen(buf)-1] == '\n') {
buf[strlen(buf)-1] = 0;
}

if ((pid = for()) < 0) {
err_sys("fork error.");
} else if (pid == 0) {
execlp(buf, buf, (char*)0);
err_ret("couldn't execute: %s", buf);
exit(127);
}

if ((pid = waitpid(pid, &status, 0)) < 0)
err_sys("waitpid error");
printf("%% ");
}

exit(0);
}

终端输入:./test

% date

回车后即显示date命令的结果了。