sample/zread.c

   1 #include <config.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4
   5 /* Trivial example of reading a gzip'ed file or gzip'ed standard input
   6  * using stdio functions fread(), getc(), etc... fseek() is not supported.
   7  * Modify according to your needs. You can easily construct the symmetric
   8  * zwrite program.
   9  *
  10  * Usage: zread [file[.gz]]
  11  * This programs assumes that gzip is somewhere in your path.
  12  */
  13 int
  14 main (int argc, char **argv)
  15 {
  16     FILE *infile;
  17     char cmd[256];
  18     char buf[BUFSIZ];
  19     int n;
  20
  21     if (argc < 1 || argc > 2) {
  22         fprintf(stderr, "usage: %s [file[.gz]]\n", argv[0]);
  23         exit(EXIT_FAILURE);
  24     }
  25     strcpy(cmd, "gzip -dc ");  /* use "gzip -c" for zwrite */
  26     if (argc == 2) {
  27         strncat(cmd, argv[1], sizeof(cmd)-strlen(cmd));
  28     }
  29     infile = popen(cmd, "r");  /* use "w" for zwrite */
  30     if (infile == NULL) {
  31         fprintf(stderr, "%s: popen('%s', 'r') failed\n", argv[0], cmd);
  32         exit(EXIT_FAILURE);
  33     }
  34     /* Read one byte using getc: */
  35     n = getc(infile);
  36     if (n == EOF) {
  37         pclose(infile);
  38         exit(EXIT_SUCCESS);
  39     }
  40     putchar(n);
  41
  42     /* Read the rest using fread: */
  43     for (;;) {
  44         n = fread(buf, 1, BUFSIZ, infile);
  45         if (n <= 0) break;
  46         fwrite(buf, 1, n, stdout);
  47     }
  48     if (pclose(infile) != 0) {
  49         fprintf(stderr, "%s: pclose failed\n", argv[0]);
  50         exit(EXIT_FAILURE);
  51     }
  52     exit(EXIT_SUCCESS);
  53     return 0; /* just to make compiler happy */
  54 }