Solved

2 children , 2 jobs with execv

Posted on 2011-03-25
3
480 Views
Last Modified: 2013-12-26
a parent process creates 2 children.
child1: ls
child2: ask for 2 numbers, and add them
but output is not what I really expect...
#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>

int main()
{
int pid1, pid2;
char* args[] = {"/bin/ls",(char*)0};
      p1=fork();
      if(p1!=0){
                printf("\n parent");
                wait(0);
      }
      else{//1st child
                 p2=fork();
                 if(p2!=0){//1st child
                           printf("\n result of ls is..\n ");
                           execv("/bin/ls",args);
                           wait(0);
                           exit(0);
                           }

                 else{//2nd child
                     printf("\n give 2 ints separ. with space \n");
                     scanf("%d  %d",&a,&b);
                     c=a+b;
                     printf("\n summ of the 2 numbers is: %d\n",c);
                     exit(0);
                 }//end 2nd child
      }//end 1st child
      return 0;
}//end main 

Open in new window

0
Comment
Question by:dimi67
  • 2
3 Comments
 
LVL 84

Accepted Solution

by:
ozo earned 500 total points
ID: 35213871
p1, p2, a, b, c are undeclared

/bin/ls is closing stdin
either dup it or
               pid2=fork();
                 if(pid2!=0){//1st child                                                    
                   wait(0);
                   printf("\n result of ls is..\n ");
                   execv("/bin/ls",args);
                   exit(0);
                 }
                 else{//2nd child                                                          
                   int a,b,c;                                                            
                   printf("\n give 2 ints separ. with space \n");
                   scanf("%d  %d",&a,&b);
                   c=a+b;
                   printf("\n summ of the 2 numbers is: %d\n",c);
                   exit(0);
0
 

Author Comment

by:dimi67
ID: 35214082
what do you mean "/bin/ls is closing stdin"? It means I cannot read from keyboard?
And why dup it?
0
 
LVL 84

Expert Comment

by:ozo
ID: 35214195
          o   The child process has its own copy of the parent's descriptors.
               These descriptors reference the same underlying objects, so
               that, for instance, file pointers in file objects are shared
               between the child and the parent, so that an lseek(2) on a
               descriptor in the child process can affect a subsequent read or
               write by the parent.
0

Featured Post

Master Your Team's Linux and Cloud Stack

Come see why top tech companies like Mailchimp and Media Temple use Linux Academy to build their employee training programs.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
List out all word 7 295
"uptime" high (200+) on RHEL6 but CPU usage is low... any ideas why? 4 106
java ^ examples 8 67
tripleUp challenge 7 79
Here is how to use MFC's automatic Radio Button handling in your dialog boxes and forms.  Beginner programmers usually start with a OnClick handler for each radio button and that's just not the right way to go.  MFC has a very cool system for handli…
The purpose of this article is to demonstrate how we can upgrade Python from version 2.7.6 to Python 2.7.10 on the Linux Mint operating system. I am using an Oracle Virtual Box where I have installed Linux Mint operating system version 17.2. Once yo…
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
Email security requires an ever evolving service that stays up to date with counter-evolving threats. The Email Laundry perform Research and Development to ensure their email security service evolves faster than cyber criminals. We apply our Threat…

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question