fileops/hexdump.c

   1 /*
   2  * Compile with:
   3  * gcc hexdump.c -o hexdump -Wall -W -Wextra -ansi -pedantic
   4 */
   5
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>    /* for memset() */
   9 #include <getopt.h>    /* FIXME: make it portable */
  10
  11 /* Function prototypes */
  12 void diep(const char *s);
  13 void dieu(const char *pname);
  14
  15 #define BUFSIZE 20    /* Must be dividable by 2 */
  16
  17 int main(int argc, char *argv[])
  18 {
  19     unsigned char buf[BUFSIZE + 1];    /* +1 for the '\0' */
  20     FILE *fp;
  21     int caps, cnt, i, j, len, opt, skip;
  22     int readbytes, totalbytes;
  23     char *fpath;
  24
  25     /* Parse arguments */
  26     caps = 0;
  27     len = -1;
  28     skip = 0;
  29     fpath = NULL;
  30     while ((opt = getopt(argc, argv, "Cn:s:f:")) != -1) {
  31         switch (opt) {
  32         case 'C':
  33             caps = 1;
  34             break;
  35         case 'n':
  36             len = atoi(optarg);
  37             break;
  38         case 's':
  39             skip = atoi(optarg);
  40             break;
  41         case 'f':
  42             fpath = optarg;
  43             break;
  44         default:    /* '?' */
  45             dieu(argv[0]);
  46         }
  47     }
  48
  49     /* optind shows to the argv[] index of the first non-option element */
  50     if (optind < argc) {
  51         fprintf(stderr, "non-option argv[]-elements: ");
  52         while (optind < argc)
  53             fprintf(stderr, "%s ", argv[optind++]);
  54         fprintf(stderr, "\n");
  55         exit(EXIT_FAILURE);
  56     }
  57
  58     if (fpath == NULL)
  59         dieu(argv[0]);
  60
  61     /* Open file */
  62     if ((fp = fopen(fpath, "r")) == NULL)
  63         diep("open");
  64
  65     /* Skip `skip' bytes */
  66     fseek(fp, skip, SEEK_SET);
  67
  68     /* Loop */
  69     cnt = 0;
  70     totalbytes = 0;
  71     while(!feof(fp) && (totalbytes < len || len == -1)) {
  72         /* Initialize buffer */
  73         memset(buf, 0, BUFSIZE);
  74
  75         /* Read `BUFSIZE' elements of 1 byte long from file */
  76         readbytes = fread(buf, 1, BUFSIZE, fp);
  77
  78         /* Print buffer */
  79         printf(caps == 1 ? "%08lX " : "%08lx ", (unsigned long)cnt * BUFSIZE + skip);
  80         for (i = 0; i < readbytes && (totalbytes < len || len == -1); i++, totalbytes++) {
  81             printf(caps == 1 ? "%02X " : "%02x ", buf[i]);
  82             if (i == (BUFSIZE / 2) - 1)
  83                 printf(" ");
  84         }
  85
  86         /* Fill in the blanks */
  87         for (j = 0; j < (BUFSIZE - i); j++) {
  88             printf("   ");
  89             if (j == (BUFSIZE/2) - 1)
  90                 printf(" ");
  91         }
  92
  93         /*
  94          * Print the output characters in the default character set.
  95          * Nonprinting characters are displayed as a single `.'
  96          */
  97         printf(" |");
  98         for (j = 0; j < i; j++) {
  99             if (buf[j] >= 32 && buf[j] <= 127)
 100                 printf("%c", buf[j]);
 101             else
 102                 printf(".");
 103         }
 104         printf("|");
 105
 106         /* New line */
 107         printf("\n");
 108
 109         cnt++;
 110     }
 111
 112     /* Close device file */
 113     (void)fclose(fp);
 114
 115     return EXIT_SUCCESS;
 116 }
 117
 118 void diep(const char *s)
 119 {
 120     perror(s);
 121     exit(EXIT_FAILURE);
 122 }
 123
 124 void dieu(const char *pname)
 125 {
 126     fprintf(stderr, "Usage: %s [-C] [-n length] [-s skip] -f file\n", pname);
 127     exit(EXIT_FAILURE);
 128 }