linux 进程 fork wait函数

fork：创建子进程

wait：父进程等待子进程结束，并销毁子进程，如果父进程不调用wait函数，子进程就会一直留在linux内核中，变成了僵尸进程。

fork函数的详细说明：fork

wait函数详细说明参考：wait

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <wait.h>//wait function
int main(){
  pid_t pid;
  pid = fork();
  if(pid == 0){
    printf("child process : %d\n", getpid());
    //exit(0);
  }
  else{
    int status;
    pid_t waitpid;
    printf("parent process : childpid=%d , mypid=%d\n",pid, getpid());
    waitpid = wait(&status);
    printf("waitpid:%d\n", waitpid);
  }
  printf("end pid: %d\n", getpid());
  return 0;
}

github源代码

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
int main(){
  pid_t pid;
  int i = 100;
  pid = fork();
  if(pid == 0){
    printf("child process : %d\n", getpid());
    i += 500;
  }
  else{
    printf("parent process : childpid=%d , mypid=%d\n",pid, getpid());
    i += 1024;
  }
  printf("i=%d\n", i);
  return 0;
}

github源代码

#include <stdio.h>
#include <unistd.h>//sleep function
#include <pthread.h>
int global_val = 0;
void* sub_thread(void *data){
  int* val = (int*)data;
  printf("sub_thread : val=%d\n", *val);
  for(int i = 0; i < 10; ++i){
    global_val++;
    printf("sub_thread : i=%d, g=%d\n", i, global_val);
    sleep(1);
  }
  return NULL;
}
int main(){
  pthread_t th;
  void* th_ret;
  int arg = 200;
  
  if(pthread_create(&th, NULL, sub_thread, (void*)&arg) != 0){
    perror("pthread_create");
    return 1;
  }
  for(int i = 0; i < 10; ++i){
    global_val++;
    printf("main: i=%d, g=%d\n", i, global_val);
    sleep(1);
  }
  if(pthread_join(th, &th_ret) != 0){
    perror("pthread_join");
    return 1;
  }
  return 0;
}

github源代码

编译时需要加 -pthread

g++ -g process-5-thread.cpp -std=c++11 -pthread