commands/cmp/cmp.c

   1 /* cmp - compare two files              Author: Kees J. Bot.  */
   2
   3 #include <sys/types.h>
   4 #include <fcntl.h>
   5 #include <stdlib.h>
   6 #include <unistd.h>
   7 #include <stdio.h>
   8 #include <string.h>
   9 #include <errno.h>
  10
  11 void fatal(char *label);
  12 int cmp(int fd1, int fd2);
  13 void Usage(void);
  14 int main(int argc, char **argv);
  15
  16 #define BLOCK   4096
  17
  18 static int loud = 0, silent = 0;
  19 static char *name1, *name2;
  20
  21 int main(argc, argv)
  22 int argc;
  23 char **argv;
  24 {
  25   int fd1, fd2;
  26
  27   /* Process the '-l' or '-s' option. */
  28   while (argc > 1 && argv[1][0] == '-' && argv[1][1] != 0) {
  29         if (argv[1][2] != 0) Usage();
  30
  31         switch (argv[1][1]) {
  32         case '-':
  33                 /* '--': no-op option. */
  34                 break;
  35         case 'l':
  36                 loud = 1;
  37                 break;
  38         case 's':
  39                 silent = 1;
  40                 break;
  41         default:
  42                 Usage();
  43         }
  44         argc--;
  45         argv++;
  46   }
  47   if (argc != 3) Usage();
  48
  49   /* Open the first file, '-' means standard input. */
  50   if (argv[1][0] == '-' && argv[1][1] == 0) {
  51         name1 = "stdin";
  52         fd1 = 0;
  53   } else {
  54         name1 = argv[1];
  55         if ((fd1 = open(name1, 0)) < 0) fatal(name1);
  56   }
  57
  58   /* Second file likewise. */
  59   if (argv[2][0] == '-' && argv[2][1] == 0) {
  60         name2 = "stdin";
  61         fd2 = 0;
  62   } else {
  63         name2 = argv[2];
  64         if ((fd2 = open(name2, 0)) < 0) fatal(name2);
  65   }
  66
  67   exit(cmp(fd1, fd2));
  68 }
  69
  70 int cmp(fd1, fd2)
  71 int fd1, fd2;
  72 {
  73   static char buf1[BLOCK], buf2[BLOCK];
  74   int n1 = 0, n2 = 0, i1 = 0, i2 = 0, c1, c2;
  75   off_t pos = 0, line = 1;
  76   int eof = 0, differ = 0;
  77
  78   for (;;) {
  79         if (i1 == n1) {
  80                 pos += n1;
  81
  82                 if ((n1 = read(fd1, buf1, sizeof(buf1))) <= 0) {
  83                         if (n1 < 0) fatal(name1);
  84                         eof |= 1;
  85                 }
  86                 i1 = 0;
  87         }
  88         if (i2 == n2) {
  89                 if ((n2 = read(fd2, buf2, sizeof(buf2))) <= 0) {
  90                         if (n2 < 0) fatal(name2);
  91                         eof |= 2;
  92                 }
  93                 i2 = 0;
  94         }
  95         if (eof != 0) break;
  96
  97         c1 = buf1[i1++];
  98         c2 = buf2[i2++];
  99
 100         if (c1 != c2) {
 101                 if (!loud) {
 102                         if (!silent) {
 103                                 printf("%s %s differ: char %ld, line %ld\n",
 104                                        name1, name2, pos + i1, line);
 105                         }
 106                         return(1);
 107                 }
 108                 printf("%10ld %3o %3o\n", pos + i1, c1 & 0xFF, c2 & 0xFF);
 109                 differ = 1;
 110         }
 111         if (c1 == '\n') line++;
 112   }
 113   if (eof == (1 | 2)) return(differ);
 114   if (!silent) fprintf(stderr, "cmp: EOF on %s\n", eof == 1 ? name1 : name2);
 115   return(1);
 116 }
 117
 118 void fatal(label)
 119 char *label;
 120 {
 121   if (!silent) fprintf(stderr, "cmp: %s: %s\n", label, strerror(errno));
 122   exit(2);
 123 }
 124
 125 void Usage()
 126 {
 127   fprintf(stderr, "Usage: cmp [-l | -s] file1 file2\n");
 128   exit(2);
 129 }