#include <sys/types.h>  /* include this before any other sys headers */ 
#include <sys/wait.h>   /* header for waitpid() and various macros */ 
#include <signal.h>     /* header for signal functions */ 
#include <stdio.h>      /* header for fprintf() */ 
#include <unistd.h>     /* header for fork() */ 
 
void  ChildProcess(void);                /* child process prototype  */ 
void  ParentProcess(void);               /* parent process prototype */
 
int  main(void) 
{     pid_t pid;

    while(1){ 
            int rc;
            // I don't think this is standard C behaviour, execpt if you want to
            // bit-shift left an uninitialized variable
            rc<<system("ps ux | awk '/mplayer/ && !/awk/ {print $2}'"); 
            [color=blue]// Where did that come from?
          rc = WEXITSTATUS(rc); /* Check if mplayer is running */ 
       if(rc >= 0 ){ 
              pid = fork();
              if(pid>=0){     
                if (pid == 0)  
                 ChildProcess(); 
                else  
                 ParentProcess(); 
                } 
              } 
       else 
          {/*fork error*/}
   
     }
return (0); 
} 
 
void  ChildProcess(void) 
{ 
     execvp("mplayer ~/test.avi",NULL); 
     exit(0); 
} 
 
void  ParentProcess(void) 
{ 
    sleep(2); 
    return; 
}

initialize
pid=fork
if(pid==0)
    exit //parent
else
    while(1)
        do something