Reputation: 187

Passing information between two seperate programs

I want to pass a value of an input variable in my program lets say#1 to another program #2 and i want #2 to print the data it got to screen, both are needed to be written in c++. The this will be on Linux.

Upvotes: 2

Answers (10)

Icextor

Reputation: 1

For a very dirt and completely nonprofessional solution you can do it like me.

Save the variable in to a file and then read it (in an infinite loop every x time) with the other program.

fsexample.open("F:/etc etc ...");
fsexample >> data1 >> data2; // etc etc

and on the other side

fsexample.open("F:/etc etc ...");
fsexample << data1 << data2; // etc etc

The trick is that F is a virtual drive created with ramdisk so it is fast and heavy-duty proof.

You could have problem of simultaneous access but you can check it with

if (!fsexample.is_open()) {
    fsexample_error = 1;
}

and retry on failure.

Upvotes: 0

anon

Reputation:

In response to your comment to Roopesh Majeti's answer, here's a very simple example using environment variables:

First program:

// p1.cpp - set the variable
#include <cstdlib>
using namespace std;;    
int main() {
    _putenv( "MYVAR=foobar" );
    system( "p2.exe" );
}

Second program:

// p2.cpp - read the variable
#include <cstdlib>
#include <iostream>
using namespace std;;

int main() {
    char * p = getenv( "MYVAR" );
    if ( p == 0 ) {
        cout << "Not set" << endl;
    }
    else {
        cout << "Value: " << p << endl;
    }
}

Note:

there is no standard way of setting an environment variable
you will need to construct the name=value string from the variable contents

Upvotes: 0

vitaly.v.ch

Reputation: 2532

DBUS
QtDbus
DBus-mm

Upvotes: 1

rui

Reputation: 11284

I think most of the answers have address the common IPC mechanisms. I'd just like to add that I would probably go for sockets because it's fairly most standard across several platforms. I decided to go for that when I needed to implement IPC that worked both on Symbian Series 60 and Windows Mobile.

The paradigm is straightforward and apart from a few platform glitches, the model worked the same for both platforms. I would also suggest using Protocol Buffers to format the data you send through. Google uses this a lot in its infrastructure. http://code.google.com/p/protobuf/

Upvotes: 1

Roopesh Majeti

Reputation: 554

If the data to be passed is just a variable, then one of the option is to set it as Environment Variable [ Var1 ] by program #1 and access it, in Program #2 [ if both are running on same env/machine ]. Guess this will be the easiest one, instead of making it complex, by using IPC/socket etc.

Upvotes: 1