src/examples/cmp.c

   1 /* cat.c
   2
   3    Compares two files. */
   4
   5 #include <stdio.h>
   6 #include <syscall.h>
   7
   8 int
   9 main (int argc, char *argv[])
  10 {
  11   int fd[2];
  12
  13   if (argc != 3)
  14     {
  15       printf ("usage: cmp A B\n");
  16       return 1;
  17     }
  18
  19   /* Open files. */
  20   fd[0] = open (argv[1]);
  21   if (fd[0] < 0)
  22     {
  23       printf ("%s: open failed\n", argv[1]);
  24       return 1;
  25     }
  26   fd[1] = open (argv[2]);
  27   if (fd[1] < 0)
  28     {
  29       printf ("%s: open failed\n", argv[1]);
  30       return 1;
  31     }
  32
  33   /* Compare data. */
  34   for (;;)
  35     {
  36       int pos;
  37       char buffer[2][1024];
  38       int bytes_read[2];
  39       int min_read;
  40       int i;
  41
  42       pos = tell (fd[0]);
  43       bytes_read[0] = read (fd[0], buffer[0], sizeof buffer[0]);
  44       bytes_read[1] = read (fd[1], buffer[1], sizeof buffer[1]);
  45       min_read = bytes_read[0] < bytes_read[1] ? bytes_read[0] : bytes_read[1];
  46       if (min_read == 0)
  47         break;
  48
  49       for (i = 0; i < min_read; i++)
  50         if (buffer[0][i] != buffer[1][i])
  51           {
  52             printf ("Byte %d is %02hhx ('%c') in %s but %02hhx ('%c') in %s\n",
  53                     pos + i,
  54                     buffer[0][i], buffer[0][i], argv[1],
  55                     buffer[1][i], buffer[1][i], argv[2]);
  56             return 1;
  57           }
  58
  59       if (min_read < bytes_read[1])
  60         printf ("%s is shorter than %s\n", argv[1], argv[2]);
  61       else if (min_read < bytes_read[0])
  62         printf ("%s is shorter than %s\n", argv[2], argv[1]);
  63     }
  64
  65   printf ("%s and %s are identical\n", argv[1], argv[2]);
  66
  67   return 0;
  68 }