/*
* This code is just to give you some familiarity about system programming.
* This gives you an insight of how to fork a process and execute UNIX commands from within a C program (Simple Shell)
*/


#include <stdio.h>
#include <sys/types.h>
#include <errno.h>
#include <unistd.h>

void parse( char *buffer, char **args);
void execute( char **args);

main(){
  char buffer[1024];
  char *args[32];
  
  while( 1 ){
    printf("\n->");    
    if( scanf("%s", buffer) == NULL ){
      printf("->");
      exit( 0 ); 
    }
    parse( buffer, args );
    execute( args );
      
 
  } 
}

void parse( char *buffer, char **args ){
  while( *buffer != NULL ){
    while( (*buffer == ' ') || (*buffer == '\t'))
      *buffer++ = NULL;

    *args++ = buffer;

    while( (*buffer != NULL) && (*buffer != ' ') && (*buffer != '\t'))
      buffer++; 
  }
  *args = NULL;    
}

void execute( char **args ){
  int pid, status;

  pid = fork();

  switch(pid) {
  case EAGAIN:
    perror("Error EAGAIN: ");
    return;
  case ENOMEM:
    perror("Error ENOMEM: ");
    return;
  }
 
  if( pid == 0 ){
    execvp(*args, args);
    perror(*args);
    exit(1);
  }
  while(wait(&status) != pid);
    
}