Why doesnt this program terminate?

This is a discussion on Why doesnt this program terminate? within the C Programming forums, part of the General Programming Boards category; Hi! I'm a complete c noob and I'm trying to get do a lab assignment for uni. What I don't ...

  1. #1
    Registered User
    Join Date
    Nov 2007
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    3

    Why doesnt this program terminate?

    Hi!

    I'm a complete c noob and I'm trying to get do a lab assignment for uni. What I don't understand at the moment is why the following code doesn't terminate, even though I use exit() ?

    Code:
    pid_t child_PID;		/* Process-ID of child */
    
    int main( int argc, char *argv[] )
    {
    
    	int status;
    
    	child_PID = fork();
    	if( -1 == child_PID )
    	{
    		fprintf( stderr, "Failed to fork" );
    		exit( 1 );
    	}
    
    	if( 0 == child_PID )
    	{
    		execlp("printenv", "printenv", NULL );
    	}
    
    	child_PID = wait( &status);
    	if( -1 == child_PID )
    	{
    		perror( "wait() failed unexpectedly, exiting");
    		exit( 1 );
    	}
    
    	/* Child process finished */
    	if( WIFEXITED( status ) )
    	{
    		int child_status = WEXITSTATUS( status );
    		if(  0 != child_status )
    		{
    			fprintf( stderr, "Child (pid %ld) failed with exit code %d\n",
    				(long int) child_PID, child_status );
    
    			exit( 1 );
    		}
    		else
    		{
    			fprintf( stderr, "child finished normally\n" );
    		}
    	}
    	else
    	{
    		/* Child process interrupted by signal */
    		if( WIFSIGNALED( status ) )
    		{
    			int child_signal = WTERMSIG( status );
    
    			fprintf( stderr, "Child (pid %ld) was terminated by signal no. %d\n",
    			(long int) child_PID, child_signal );
    			exit( 1 );
    		}
    	}
    	exit( 0 );
    }

  2. #2
    Kernel hacker
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    Farncombe, Surrey, England
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    Seeing as there is no loops in the code, I fail to see how it could not terminate... Does it perform "printenv" correctly?

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Registered User
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    Nov 2007
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    3
    Sorry, my bad I ran it through another program which isi the one that doesnt terminate.

    Thx anyway :-)

    //T

  4. #4
    Kernel hacker
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    Location
    Farncombe, Surrey, England
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    So, what you are saying is that YOUR application works OK as it's posted here, but if the application instead of "printenv" doesn't terminate, neither does yours [naturally, as it's waiting for that application to terminate]?

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  5. #5
    Registered User
    Join Date
    Nov 2007
    Posts
    3
    Something like that.

    This is our first real programming assignment in c, and so our teachers have kindly supplied us with a small program called runsafe which terminates all child processes after a set amount of time so that we dont leave a bunch of unfinished processes every time we execute our unfinished programs:-)

    This is the program that does not terminate (until the set time). I thought it was my program that didn't terminate and that runsafe had to kill it.

    //T

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