#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

#define MAX_STRING	30
#define MAX_MESSAGES    100
#define FIFO_NAME	"buffer"

void Child( void );
void Parent( void );
void Error( char* sPrefix );


int main( void )
{
    if ( mknod( FIFO_NAME, S_IFIFO | 0600, 0 ) < 0 )
        Error( "mknod" );
     
    setbuf( stdout, NULL );

    if ( 0 == fork() )
        Child();
    else  {
        Parent();
        wait( 0 );

        unlink( FIFO_NAME );
    }
}

void Child( void )
{
    char sBuffer[ MAX_STRING ];
    int  fd = open( FIFO_NAME, O_RDWR ),
         i;

    if ( fd < 0 )
        Error( "child fifo open" );

    for ( i = 1; i <= MAX_MESSAGES; ++i )  {
        sprintf( sBuffer, "Line number %d", i );
        printf( "Child sending '%s'\n", sBuffer );

        if ( write( fd, sBuffer, MAX_STRING ) < 0 )
            Error( "child write" );

        /* sleep every now and then... */
        if ( 0 == ( i % 25 ) )
            sleep( 1 );
    }

    close( fd );
}

void Parent( void )
{
    char sBuffer[ MAX_STRING ];
    int  fd = open( FIFO_NAME, O_RDWR ),
         i;

    if ( fd < 0 )
        Error( "parent fifo open" );

    for ( i = 0; i < MAX_MESSAGES; ++i )  {
        if ( read( fd, sBuffer, MAX_STRING ) < 0 )
            Error( "parent read" );

        printf( "Parent got '%s'\n", sBuffer );

        /* sleep every now and then */
        if ( 0 == ( i % 20 ) )
            sleep( 1 );
    }
}

void Error( char* sPrefix )
{
    perror( sPrefix );
    exit( EXIT_FAILURE );
}