复制进程fork
1.fork方法
用man命令查看fork方法
wys@DESKTOP-2OU3HRV:~/mycode/day08$ man fork
pid_t fork(void)；
函数返回类型 pid_t 实质是 int 类型
fork 函数会新生成一个进程，调用 fork 函数的进程为父进程，新生成的进程为子进程。
在父进程中返回子进程的 pid，在子进程中返回 0，失败返回-1。
编写以下程序：
1 #include<stdio.h>
2 #include<stdlib.h>
3 #include<assert.h>
4 #include<unistd.h>
5 #include<string.h>
6 int main()
7 {
8 char* s = NULL;
9 int n = 0;
10
11 pid_t pid = fork();
12 assert(pid != -1);
13
14 if(pid == 0)
15 {
16 s = "child";
17 n = 3;
18 }
19 else
20 {
21 s = "parent";
22 n = 7;
23 }
24
25 for(int i = 0;i < n;i++)
26 {
27 printf("n = %d,&n = %p,s = %s,pid = %d\n",n,&n,s,getpid());
28 sleep(1);
29 }
30
31 exit(0);
32 }
编译运行：
wys@DESKTOP-2OU3HRV:~/mycode/day08$ gcc main.c -o main
wys@DESKTOP-2OU3HRV:~/mycode/day08$ ls
main main.c
wys@DESKTOP-2OU3HRV:~/mycode/day08$ ./main
n = 7,&n = 0x7fffd7ddbe34,s = parent,pid = 206
n = 3,&n = 0x7fffd7ddbe34,s = child,pid = 207
n = 7,&n = 0x7fffd7ddbe34,s = parent,pid = 206
n = 3,&n = 0x7fffd7ddbe34,s = child,pid = 207
n = 7,&n = 0x7fffd7ddbe34,s = parent,pid = 206
n = 3,&n = 0x7fffd7ddbe34,s = child,pid = 207
n = 7,&n = 0x7fffd7ddbe34,s = parent,pid = 206
n = 7,&n = 0x7fffd7ddbe34,s = parent,pid = 206
n = 7,&n = 0x7fffd7ddbe34,s = parent,pid = 206
n = 7,&n = 0x7fffd7ddbe34,s = parent,pid = 206
wys@DESKTOP-2OU3HRV:~/mycode/day08$
注：父进程和子进程并发执行
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