Question

这是我编写的示例程序，用于理解终端中的执行工作 program1.c

#include<stdio.h>
#include<unistd.h>
#include <stdlib.h>

int main()
{
     int i;
     printf("Checking out linux working details 2\n");
     pid_t pid=fork();
     return 0;

}

现在请您解释一下bash，ps，sh进程的状态（即他们的pid等）。这是样本运行

运行：

$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4496  4488  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 R  1000  4506  4496  0  80   0 -  3561 -      pts/2    00:00:00 ps

$ gcc program1.c
$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4496  4488  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 R  1000  4513  4496  0  80   0 -  3561 -      pts/2    00:00:00 ps

$ ./a.out
Checking out linux working details 2

$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4496  4488  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 R  1000  4516  4496  0  80   0 -  3561 -      pts/2    00:00:00 ps

$ ./a.out
Checking out linux working details 2

$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4496  4488  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 R  1000  4519  4496  0  80   0 -  3561 -      pts/2    00:00:00 ps

program2.c

#include<stdio.h>
#include<unistd.h>
#include <stdlib.h>

int main()
{
     system("ps -l");
     return 0;
}

示例运行：

$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4592  4584  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 R  1000  4602  4592  0  80   0 -  3561 -      pts/2    00:00:00 ps

$ gcc program2.c
$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4592  4584  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 R  1000  4609  4592  0  80   0 -  3561 -      pts/2    00:00:00 ps

$ ./a.out
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4592  4584  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 S  1000  4610  4592  0  80   0 -  1055 wait   pts/2    00:00:00 a.out
0 S  1000  4611  4610  0  80   0 -  1119 wait   pts/2    00:00:00 sh
0 R  1000  4612  4611  0  80   0 -  3561 -      pts/2    00:00:00 ps

$ ps -l
F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000  4592  4584  0  80   0 -  6730 wait   pts/2    00:00:00 bash
0 R  1000  4613  4592  0  80   0 -  3561 -      pts/2    00:00:00 ps

ps：非常感谢详细的答案

Answer 1

每次运行程序时，都会创建一个具有唯一pid的新进程。这就是为什么在你的例子中bash的pid始终保持不变的原因，因为它仍然是相同的过程，并且ps的所有连续调用都有不同的。

你虽然可以看到父pid（ppid）与＆＃34; ps -l＆＃34;它显示了创建它的进程的pid（分叉）。

也许您想尝试以下代码：

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>

int main()
{
     int i;
     printf("before fork() ps -l\n");
     system("ps -l");
     pid_t pid=fork();
     if (pid < 0) {
          printf("fork-error.");
     } else if (pid == 0) {
          printf("child ps -l\n");
          system("ps -l");
     } else {
          int status;
          pid_t finished = wait(&status);
          printf("parent with child %i finished %i ps -l\n", pid, finished);
          system("ps -l");
     }
     return 0;
}

bash，sh，ps如何在linux中运行？

1 个答案: