/*******************************************************
   free.c
   CMSC-421  Fall 2004 HW 1
   Spencer Shimko

*********************************************************/
#include <fcntl.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>


#define MEMFILE "/proc/meminfo"
#define CMDOPTS "bkmots:V"

/* The description displayed by this usage function is copied 
verbatim from "free -h" to be as accurate as possible */
void show_usage(const char *self)
{
       fprintf(stderr, "usage: %s [-b|-k|-m] [-o] [-t] [-s delay] [-V]\n", self);
       fprintf(stderr,"\t-b,-k,-m show output in bytes, KB, or MB\n");
       fprintf(stderr,"\t-o use old format (no -/+buffers/cache line)\n");
       fprintf(stderr,"\t-t display total for RAM + swap\n");
       fprintf(stderr,"\t-s update every [delay] seconds\n");
       fprintf(stderr,"\t-V display version information and exit\n");
}

/* Begin main */
int main( int argc, char **argv ){
   char arg;
   FILE *memfile;
   unsigned long total, used, free, shared, buffers, cached, bufncache, swap_total, swap_used, swap_free;
   int delay = 0; /* no delay by default */ 
   int f_old = 0, f_ttl = 0; /* no flags by default */
   int posshift = 10; /* default output is in KB */
   
   /* parse command line */
   while ( ( arg = getopt ( argc, argv, CMDOPTS ) ) != EOF ) {
      switch ( arg ){
         case 'b':
            posshift = 0;
            break;
         case 'k':
            posshift = 10;
            break;
         case 'm':
            posshift = 20;
            break;
         case 'o': 
            f_old = 1;
            break;
         case 't':
            f_ttl = 1;
            break;
         case 's': 
            delay = 1000000 * atof ( optarg );
            break;
         case 'V': 
            printf( "Spencer's free implementation v0.1\n" );
            return 0;
         default:
            show_usage ( argv[0] );
            return 1;
      }
   }

   if ( optind < argc ) {
      show_usage ( argv[0] );
      return 1;
   }

   do {
      memfile = fopen( MEMFILE, "r"); 

      /* open a text file for reading */
      if ( memfile == NULL ) {
         fprintf(stderr, "Fatal Error: can't open %s\nIs /proc filesystem mounted?\n", MEMFILE );
         return 1;
      }
      else {
         fscanf(memfile, "        total:    used:    free:  shared: buffers:  cached:\nMem:%lu%lu%lu%lu%lu%lu\nSwap:%lu%lu%lu", 
               &total, &used, &free,&shared, &buffers, &cached, &swap_total, &swap_used, &swap_free );
         fclose(memfile);

         printf("             total       used       free     shared    buffers     cached\n");
      
         /* print formatting strings are all altered forms of those found in procps
          * they are not copied */
         printf("%-7s %10lu %10lu %10lu %10lu %10lu %10lu\n", "Mem:", 
               total >> posshift, used >> posshift, free >> posshift, 
               shared >> posshift, buffers >> posshift, cached >> posshift);

         if ( ! f_old ) {
            bufncache = buffers + cached;
            printf(
                  "-/+ buffers/cache: %10lu %10lu\n", 
                  (used - bufncache) >> posshift, 
                  (free + bufncache) >> posshift);
         }

         /* swap info is printed regardless of flags */
         printf(
              "%-7s %10lu %10lu %10lu\n", "Swap:",
              swap_total >> posshift, swap_used >> posshift, swap_free >> posshift);
         
         if ( f_ttl ){
            printf ( "%-7s %10lu %10lu %10lu\n", "Total:",
                  ( total + swap_total ) >> posshift,
                  ( used + swap_used ) >> posshift,
                  ( free + swap_free ) >> posshift );
         }

         if ( delay ){
          /*  fputc('\n', stdout);
            fflush(stdout);
            if ( usleep(delay) == -1 ){
               fprintf(stderr, "Error processing delay!\n");
               return 1;
            }
         */
         }
      } 
   } while ( delay );
   return 0;
}