system

#include
#include
#include
#include

int system(const char * cmdstring)
...{
    pid_t pid;
    int status;

    if(cmdstring == NULL)...{
        return (1);
    }

    if((pid = fork())<0)...{
        status = -1;
    }
    else if(pid == 0)...{  //子进中运行脚本命令
        execl("/bin/sh", "sh", "-c", cmdstring, (char *)0);
        -exit(127); //子进程正常执行则不会执行此语句
    }
    else...{  //父进程中等待子进程返回
            while(waitpid(pid, &status, 0) < 0)...{
                if(errno != EINTER)...{
                    status = -1;
                    break;
                }
            }
    }
    return status;
}