程序清单 8-8 exec函数实例，a.out是程序8-9产生的可执行程序

 /*
  ============================================================================
  Name        : test.c
  Author      : blank
  Version     :
  Copyright   : Your copyright notice
  Description : 程序清单 8-8 exec函数实例，a.out是程序8-9产生的可执行程序============================================================================
 */

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

 char *evn_init[] = { "USER=unknown", "PATH=/tmp", NULL};
 int main(int argc, char *argv[])
 {
     pid_t pid;

     if ((pid = fork()) < ){
         err_sys("fork error");
     }else if (pid == ){
         // specify pathname, specify environment
         if (execle("/home/blank/workspace/test/src/a.out", "a.out", "myarg1",
                 "MY ARG2", (char *), evn_init) < ){
             err_sys("execel error");
         }
     }

     if (waitpid(pid, NULL, ) < ){
         err_sys("waitpid error");
     }

     if ((pid = fork()) < ){
         err_sys("fork error");
     }else if (pid == ){
         // specify filename, inherit environment
         if (execlp("./a.out", "a.out", "only 1 arg", (char *)) < ){
             err_sys("execlp error");
         }
     }

     exit();
 }