linux system 函數的實現源碼

system函數的實現源碼，看到父進程是在子進程執行完成之後才繼續往下走，否則一直掛在那等的子進程執行完。

 

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){
        execl("/bin/sh", "sh", "-c", cmdstring, (char *)0);
        -exit(127); //子進程正常執行則不會執行此語句

        }
    else{
            while(waitpid(pid, &status, 0) < 0){
                if(errno != EINTER){
                    status = -1;
                    break;
                }
            }
        }
        return status;
}


 驗證：

#include <stdio.h>
#include <stdlib.h>
int main(){
        system("sleep 3");
        printf("after system()");
        return 0;
}


 

因此，以上推論是正確的