Thread: Trouble with fork() & alarm()...

Hi all,

After countless hours going over my code I have no idea why it doesn't want to work...

I'm trying to use fork() to print two messages for 5 seconds each using alarm() to swap the active process to the other.
When I run my code it prints the [Parent] message alone for 5 seconds, however it continues to run simultaneously when the [Child] wakes from its initial sleep.
After 5 seconds of simultaneous processing the [Parent] continues to run alone indefinately; the [Child] never returns...
This leads me to believe that the [Parent] never enters the handler function but I can't work out why...

Code:

/*  */



// Pre-processor Directives /////////////////////////////////////

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <wait.h>

/////////////////////////////////////////////////////////////////



// Function Prototypes //////////////////////////////////////////

void handler( int );

/////////////////////////////////////////////////////////////////



// Main Function Implementation /////////////////////////////////

int i, j = 1;

int main( void )
{
	if( fork() != 0 )
	{
		while( 1 )
		{
			signal( SIGALRM, handler );
			if( i == 1 )
			{
				alarm( 5 );
				i--;
			}
			printf( "[PARENT] Serving HTTP Session 2\n" );fflush( stdout );
		}
	}
	else
	{
		sleep( 5 ); /* Allow the parent to get ready. */
		while( 1 )
		{
			signal( SIGALRM, handler );
			if( j == 1 )
			{
				alarm( 5 );
				j--;
			}
			printf( "[CHILD] Serving HTTP Session 1\n" );fflush( stdout );
		}
	}
	exit( EXIT_SUCCESS );
}

/////////////////////////////////////////////////////////////////



// Sub-function Implementation //////////////////////////////////

void handler( int SIG )
{
	if( i = 0 )
		i++;
	if( j = 0 )
		j++;
	pause(); /* Pause the process until the other process sends it's alarm signal. */
	signal( SIGALRM, handler );
}

/////////////////////////////////////////////////////////////////

Any thoughts?

Code:

int i, j = 1;

You don't initialize i.

Code:

void handler( int SIG )
{
    if( i = 0 )
        i++;
    if( j = 0 )
        j++;

You are missing a "=" in both conditions.

Bye, Andreas

Thanks! You fail to see these OBVIOUS things after too long! ;-)