Thank you all for your help.
Vijay.
On Tue, Feb 7, 2012 at 9:10 PM, Bernd Petrovitsch
<bernd@xxxxxxxxxxxxxxxxxxx> wrote:
> On Die, 2012-02-07 at 00:38 +0530, Vijay Chauhan wrote:
>> Hi List,
>>
>> I am learning Linux and trying to understand exec and fork function.
>> execl says that it overlays the running address space. What does it mean?
>>
>> I created the following program and used top command with
>> intentionally wrong arguments:
>>
>> #include<stdio.h>
>> #include<unistd.h>
>> #include<sys/types.h>
>> #include<stdlib.h>
>>
>> int main(){
>> int a = -1;
>> if(fork()==0){
>> printf("Inside child\n");
>> printf("child pid=%d, parentid=%d\n", getpid(), getppid());
>> execl("/usr/bin/top", "/usr/bin/top", ">/dev/null" ,(char*)0 );
>
> You get here only if the execl() as such fails.
>
>> scanf("inside child provide a %d", &a);
>
> You should check the return value here if you actually got a matching
> parameter.
> scanf() is actually a function to be avoided.
>
>> printf("Inside child a=%d\n", a);
>> exit(1);
>> } else {
>> printf("Inside parent, going to wait\n");
>> printf("my pid=%d, parentid=%d\n", getpid(), getppid());
>> scanf("input parent %d\n", &a);
>
> You should check the return value here if you actually got a matching
> parameter.
> scanf() is actually a function to be avoided.
>
>> wait(NULL);
>
> You should check the return value here to know why "wait()" returns.
>
>> printf("Wait over\n");
>> printf("Inside parent a=%d\n", a);
>> }
>> return 0;
>> }
>
> Bernd
> --
> Bernd Petrovitsch Email : bernd@xxxxxxxxxxxxxxxxxxx
> LUGA : http://www.luga.at
>
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