[linux] setsid测试

Posted 2022-11-29 adream307

测试程序如下

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

int main()
	printf("start...\\n");
	int err = setenv("ENV_TEST","VALUE_TEST",0);
	if(err<0) return err;
	
	int pid = fork();
	if(pid<0) return -1;
	if(pid==0)
		// if(setsid()<0)
		// 	printf("child setsid error\\n");
		// 
		for(;;)
			char *env = getenv("ENV_TEST");
			if(env!=NULL)
				pid = getpid();
				printf("child env = %s,pid = %d, pgid = %d\\n",env,pid,getpgid(pid));		
			else
				printf("child env = null\\n");
			
			sleep(1);
		
	else
		for(;;)
			char *env = getenv("ENV_TEST");
			if(env!=NULL)
				pid = getpid();
				printf("parent env = %s,pid = %d, pgid = %d\\n",env,pid,getpgid(pid));
			else
				printf("parent env = null\\n");
			
			sleep(1);
		
	
	return 0;

程序运行时在终端号打印如下信息:

 $ ./detach_process 
start...
parent env = VALUE_TEST,pid = 11015, pgid = 11015
child env = VALUE_TEST,pid = 11016, pgid = 11015
parent env = VALUE_TEST,pid = 11015, pgid = 11015

在当前终端按 CTRL-C ，可以发现父进程和子进程同时被终止

---

在子进程设置 setsid，代码如下:

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

int main()
	printf("start...\\n");
	int err = setenv("ENV_TEST","VALUE_TEST",0);
	if(err<0) return err;
	
	int pid = fork();
	if(pid<0) return -1;
	if(pid==0)
		if(setsid()<0)
			printf("child setsid error\\n");
		
		for(;;)
			char *env = getenv("ENV_TEST");
			if(env!=NULL)
				pid = getpid();
				printf("child env = %s,pid = %d, pgid = %d\\n",env,pid,getpgid(pid));		
			else
				printf("child env = null\\n");
			
			sleep(1);
		
	else
		for(;;)
			char *env = getenv("ENV_TEST");
			if(env!=NULL)
				pid = getpid();
				printf("parent env = %s,pid = %d, pgid = %d\\n",env,pid,getpgid(pid));
			else
				printf("parent env = null\\n");
			
			sleep(1);
		
	
	return 0;

程序运行时在终端号打印如下信息:

 $ ./detach_process 
start...
parent env = VALUE_TEST,pid = 11015, pgid = 11015
child env = VALUE_TEST,pid = 11016, pgid = 11015
parent env = VALUE_TEST,pid = 11015, pgid = 11015

此时在当前终端按 CTRL-C ，可以发现只有父进程被终止了，子进程依然在运行