hi,

In a c program the value of an integer variable is changing rapidly. I have to get the value of that variable at a particular instant from another program. How can i do it without using a file?

When i tried with extern variable as

prgm 1: update.c:

#include<stdio.h>
#include "header.h"

main()
{
extern int VAR_A, VAR_B;
while(1)
{
VAR_A++;
VAR_B++;
}
}

pgm 2: print.c:

#include<stdio.h>
#include "header.h"

main()
{
extern int VAR_A, VAR_B;
while(1)
{
printf("\nValue of variables are %d %d\n",VAR_A,VAR_B);
}
}

header.h:

#ifndef HEADER_H
#define HEADER_H

int VAR_A, VAR_B;

#endif

i execute the both .c file from 2 terminals but got only value 0 printed for both var_a and var_b all the time.

regards
vyshakh

extern does not mean the variable is in another program.

It typically means the variable is in another source module of the same program. But it doesn't even need to mean another source module. It could be in the same source module.

You need shared memory for the type of communication between programs that you seem to want.

A google or forum search for linux shared memory should give you many simple examples of setting up and using shared memory.

thank u very much for ur reply........

I think you can be more general than shared memory. You need to use Interprocess Communication, IPC. For a very good primer on the subject, see Beej's Guide to Unix Interprocess Communication.
This should give you enough understanding of the process to choose a method that is appropriate for your purpose, as well as enough working sample code to get you started.

--- rod.

Thank you so much! I love finding awesome Linux guides in PDF!