3.2. gdbm_list.cc

3.2.1

A little utility to list the records in a GDBM file to the standard output. The only command line argument is the name of the file. The records are not guaranteed to come out in any particular order.

3.2.2
#include "doc.hh"
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <gdbm.h>
3.2.3

Create a dynamically allocated and nicely escapped copy of the string in a `datum' object.

void
copy_datum_str (const datum &d, string &s)
{
   const char *hexdigits = "0123456789ABCDEF";

   for (size_t i = 0; i < d.dsize; ++i)
   {
      char c = d.dptr[i];

      if (c == '\\')
         s += "\\\\";
      else if (c == ':')
         s += "\\:";
      else if (c ≥ 32 && c < 127)
         s += c;
      else
      {
         switch (c)
         {
          case '\a': s += "\\a"; break;
          case '\b': s += "\\b"; break;
          case '\t': s += "\\t"; break;
          case '\n': s += "\\n"; break;
          case '\v': s += "\\v"; break;
          case '\f': s += "\\f"; break;
          case '\r': s += "\\r"; break;
          case 27: s += "\\e"; break;

          default:
            s += "\\x";
            s += hexdigits[(c / 16) & 0x0F];
            s += hexdigits[c & 0x0F];
         }
      }
   }
}
3.2.4

The main function.

int
main (int argc, char **argv)
{
3.2.5

Check command line arguments.

   if (argc ≠ 2)
   {
      fprintf (stderr, "Usage: %s FILENAME\n", argv[0]);
      return 1;
   }
3.2.6

Try to open the file.

   GDBM_FILE db = gdbm_open (argv[1], 0, GDBM_READER, 0600, NULL);
   if (db == NULL)
   {
      fprintf (stderr, "%s: unable to open GDBM file `%s': %s\n",
               argv[0], argv[1], gdbm_strerror (gdbm_errno));
      return 2;
   }
3.2.7

Sequence through the records and print them out.

   datum key = gdbm_firstkey (db);
   while (key.dptr)
   {
      datum val = gdbm_fetch (db, key);
      string keystr, valstr;
      copy_datum_str (key, keystr);
      copy_datum_str (val, valstr);
      printf ("%s:%s\n", keystr.c_str(), valstr.c_str());

      datum nextkey = gdbm_nextkey (db, key);

      free (key.dptr);
      free (val.dptr);
      key = nextkey;
   }
3.2.8

Close the DB nicely and finish.

   gdbm_close (db);
   return 0;
}