标签：cnt 0.0 pid CLC print 进程 等待 father
为什么等待子进程？
要子进程干活，检查活干完了，还是没完（abort还是被杀死了）
僵尸进程
父进程等待子进程退出 并收集子进程的退出状态
子进程退出状态不被收集，变成僵死进程（僵尸进程）
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main()
{
pid_t pid;
int cnt = 0;
pid = vfork();
if(pid > 0){
while(1){
printf("father print , pid = %d\n",getpid());
printf("cnt = %d\n",cnt);
sleep(1);
}
}else if(pid == 0){
while(1){
printf("son print , pid = %d\n",getpid());
sleep(1);
cnt++;
if(cnt == 5){
exit(0);
}
}
}
return 0;
}CLC@Embed_Learn:~/2_jingCheng$ gcc demo12.c -o newpro
CLC@Embed_Learn:~/2_jingCheng$
CLC@Embed_Learn:~/2_jingCheng$
CLC@Embed_Learn:~/2_jingCheng$ ./newpro
son print , pid = 30749
son print , pid = 30749
son print , pid = 30749
son print , pid = 30749
son print , pid = 30749
father print , pid = 30748
cnt = 5
father print , pid = 30748
cnt = 5
father print , pid = 30748
cnt = 5
father print , pid = 30748
cnt = 5
father print , pid = 30748
cnt = 5
father print , pid = 30748
cnt = 5
CLC@Embed_Learn:~$ ps -aux|grep newpro
Warning: bad ps syntax, perhaps a bogus '-'? See http://procps.sf.net/faq.html
CLC 30748 0.0 0.0 4160 428 pts/27 S+ 13:01 0:00 ./newpro
CLC 30749 0.0 0.0 0 0 pts/27 Z+ 13:01 0:00 [newpro] <defunct>
CLC 30820 0.0 0.0 13588 940 pts/31 S+ 13:02 0:00 grep --color=auto newpro
子进程pid = 30749 , Z+表示僵尸进程
相关函数
区别： waitpid使调用者阻塞，waitpid有一个选项，可以使调用者不阻塞
wait等待
include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main()
{
pid_t pid;
int status = 10;
int cnt = 0;
pid = fork();
if(pid > 0){
wait(&status);
printf("child quit, status = %d\n",WEXITSTATUS(status));
while(1){
printf("father print , pid = %d\n",getpid());
printf("cnt = %d\n",cnt);
sleep(1);
}
}else if(pid == 0){
while(1){
printf("son print , pid = %d\n",getpid());
sleep(1);
cnt++;
if(cnt == 5){
exit(3);
}
}
}
return 0;
}
CLC@Embed_Learn:~/2_jingCheng$ ./a.out
son print , pid = 30946
son print , pid = 30946
son print , pid = 30946
son print , pid = 30946
son print , pid = 30946
child quit, status = 3
father print , pid = 30945
cnt = 0
father print , pid = 30945
cnt = 0
father print , pid = 30945
cnt = 0
father print , pid = 30945
进程：没有僵尸进程
CLC@Embed_Learn:~$ ps -aux|grep ./a.out
Warning: bad ps syntax, perhaps a bogus '-'? See http://procps.sf.net/faq.html
CLC 30945 0.0 0.0 4156 348 pts/27 S+ 13:10 0:00 ./a.out
CLC 30946 0.0 0.0 4160 84 pts/27 S+ 13:10 0:00 ./a.out
CLC 30948 0.0 0.0 13588 952 pts/31 S+ 13:10 0:00 grep --color=auto ./a.out
waitpid等待
status参数： 是一个整型数指针
非空： 子进程退出状态放在它所指向的地址中。
空： 不关心退出状态
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main()
{
pid_t pid;
int status = 10;
int cnt = 0;
pid = fork();
if(pid > 0){
waitpid(pid,&status,WNOHANG);
printf("child quit, status = %d\n",WEXITSTATUS(status));
while(1){
printf("father print , pid = %d\n",getpid());
printf("cnt = %d\n",cnt);
sleep(1);
}
}else if(pid == 0){
while(1){
printf("son print , pid = %d\n",getpid());
sleep(1);
cnt++;
if(cnt == 5){
exit(3);
}
}
}
return 0;
}
CLC@Embed_Learn:~/2_jingCheng$ ./a.out
child quit, status = 0
father print , pid = 31060
cnt = 0
son print , pid = 31061
son print , pid = 31061
father print , pid = 31060
cnt = 0
son print , pid = 31061
father print , pid = 31060
cnt = 0
father print , pid = 31060
cnt = 0
son print , pid = 31061
CLC@Embed_Learn:~$ ps -aux|grep a.out
Warning: bad ps syntax, perhaps a bogus '-'? See http://procps.sf.net/faq.html
CLC 31060 0.0 0.0 4160 352 pts/27 S+ 13:19 0:00 ./a.out
CLC 31061 0.0 0.0 4160 88 pts/27 S+ 13:19 0:00 ./a.out
CLC 31063 0.0 0.0 13588 948 pts/31 S+ 13:19 0:00 grep --color=auto a.out孤儿进程
父进程如果不等待子进程退出，在子进程之前就结束了自己的“生命”，此时子进程叫做孤儿进程。
Linux避免系统存在过多孤儿进程，init进程收留孤儿进程，变成孤儿进程的父进程。
标签：cnt,0.0,pid,CLC,print,进程,等待,father 来源： https://blog.csdn.net/qq_53550531/article/details/123305869
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