using C to create a child and parent process

Question

I am making the following code in C. I am writing a program that creates a new process using fork system call. Then I want to check which one is active and finally if it's a child process return the list of all the directories within that file, or if it's a parent wait for termination of the child process.

Following is my code:

#include <stdio.h>
#include <string.h>
#include <dirent.h> 
#include <iostream>


int main(){
  int pid = fork();
  if(pid < 0){
    printf(stderr, "Fork call failed! \n");
  }
  else if(pid == 0){
    printf("This process is the child from fork=%d\n", pid);
    printf("Thecurrent file inside the directory are:\n");
    DIR *d;
    struct dirent *dir;
    d = opendir(".");
    if (d) {
      while ((dir = readdir(d)) != NULL) {
    printf("%s\n", dir->d_name);
      }
      closedir(d);
    }
    exit(0);
  }
  else{
    printf("This process is the parent from fork=%d\n", pid);
    int stats;    
    //parent process waits for child to terminate
    waitpid(pid, &stats, 0);

    if(stats == 0){
      printf("This process is terminated.");
    }

    if(stats == 1){
      printf("This process is terminated and an error has occured.");
    }
  }
  return 0;
}

fatal error: iostream: No such file or directory  #include <iostream>
                    ^ compilation terminated.

If I remove #include <iostream> , I get:

/usr/include/stdio.h:362:12: note: expected ‘const char * __restrict__’ but argument is of type ‘struct _IO_FILE *’

how can I fix this problem?

Answer 1

Your error is in the first function call to printf() :

printf(stderr, "Fork call failed! \n");

It should actually be fprintf() instead:

fprintf(stderr, "Fork call failed! \n");

---

Also, don't forget to include:

• unistd.h for fork() .
• sys/types.h and sys/wait.h for waitpid() .
• stdlib.h for exit() .

and remove #include <iostream> since that is for C++.