Thread: Vim help!

I am new to coding in C and even newer to using VIM

I am currently trying to write a code that will store PID numbers of a child after a fork, I have to be able to enter an amount that will be created, so far I have managed to be able to get them to print (which puts me on the right path as far as I am concerned) but I am having issues.

Using the following code:

Code:

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
   int prod = atoi(argv[1]);
   int count = 0;
   if(argc == 2)
   {
      while(count < prod)
      {
         printf("success\n\n");
         int i; 
         i=fork(); 
         printf("\n");  

         if(i==0) 
         {
            printf("Child printing");
            printf("getpid: %d, getppid: %d \n",getpid(), getppid()); 
         }
          count++; 
      }
   }
   else
   {
      printf("Not enough paramterers");
   }return 0;
 exit(0);
}

while this has some success, it is for some reason creating a 3rd iteration and I can't work out why

The "success" print is more of a marker, but every time I run the program I get this result:

Code:

k110-1:~ s029119a$ ./try3.exe 2
success


success



Child printinggetpid: 9335, getppid: 1 
success


k110-1:~ s029119a$ 
Child printinggetpid: 9336, getppid: 1 

Child printinggetpid: 9337, getppid: 1

Can anyone offer any advice or tell me what I'm doing wrong, why is it doing this?

you should think about what will happen in the child process when it gets to the second iteration of the loop

you probably want to wait for the child to exit

Code:

#include <unistd.h>     /* Symbolic Constants */
#include <sys/types.h>  /* Primitive System Data Types */ 
#include <errno.h>      /* Errors */
#include <stdio.h>      /* Input/Output */
#include <sys/wait.h>   /* Wait for Process Termination */
#include <stdlib.h>     /* General Utilities */
#include <time.h>

static void Usage(const char* prog)
{
    printf("Not enough arguments\n");
    printf("Usage:\n");
    printf("%s <Number>\n", prog);
    printf("\t where <Number> is number of child processes to start\n");
    return;
}
int main(int argc, char* argv[])
{
    pid_t childpid; /* variable to store the child's pid */
    int retval;     /* child process: return code */
    int status;     /* parent process: child's exit status */
    int count;
    int childs;
    
    srand(time(NULL));
    if(argc < 2)
    {
        Usage(argv[0]);
        exit(0);
    }
    childs = (int)strtol(argv[1],NULL,10);

    for(count=0; count <  childs;count++)
    {
        /* now create new process */
        childpid = fork();

        if (childpid >= 0) /* fork succeeded */
        {
            if (childpid == 0) /* fork() returns 0 to the child process */
            {
                printf("CHILD: I am the child process!\n");
                printf("CHILD: Here's my PID: %d\n", getpid());
                printf("CHILD: My parent's PID is: %d\n", getppid());
                printf("CHILD: The value of my copy of childpid is: %d\n", childpid);
                printf("CHILD: Sleeping for 1 second...\n");
                sleep(1); /* sleep for 1 second */
                retval = getpid()%255;
                printf("CHILD: Goodbye! retval=%d\n",retval);    
                exit(retval); /* child exits with random return code */
            }
            else /* fork() returns new pid to the parent process */
            {
                if(count == 0)
                {
                    printf("PARENT: I am the parent process!\n");
                    printf("PARENT: Here's my PID: %d\n", getpid());
                }
                printf("PARENT: The value of my copy of childpid is %d\n", childpid);
                    
            }
        }
        else /* fork returns -1 on failure */
        {
            perror("fork"); /* display error message */
            exit(0); 
        }
    }
    for(count=0; count <  childs;count++)
    {
        printf("PARENT: I will now wait for my child %d to exit.\n",count);
        wait(&status); /* wait for child to exit, and store its status */
        printf("PARENT: Child's exit code is: %d\n", WEXITSTATUS(status));
    }
    printf("PARENT: Goodbye!\n");             
    exit(0);  /* parent exits */   
}