: I have a requirement for a table of names/phone numbers. Basically this is a
: struct of char name[80] and char telno[30], called dataLine. I have an array
: of 100 dataLines, which is a simple phone book.
:
: Question: the "100" is totally arbitrary. The number of entries could be 10,
: or 100,000. The data file can be reloaded while the program is running to
: update the database. How can I make my array bigger if, say, someone's added
: 100 phone numbers to the file? I don't want to specify a very big arbitrary
: maximum and hope for the best, because of the huge possible range. I'd much
: rather the program increased the array size to cope.

Instead of a fixed array

  struct dataLine table[100];

use a dynamic array, managed through malloc, realloc and free

  #include <stdlib.h>

  ...

  struct dataLine *table = 0;

  ...

  table = malloc( 100 * sizeof *table );
  if ( table == 0 ) {
    /* handle error */
  }

  ...

  /* table needs to be resized */
  table = remalloc( table, new_size );
  if ( table == 0 ) {
    /* handle error */
  }

  ...

  free( table );

: Please respond by e-mail. I will post a summary of responses later.

Post here, read here.

-- Mat.

I read the FAQ list, but where does it talk about not asking for an e-mail
response?

okay to do so, provided that you post a summary (which Richard promised to
do).

Regards,

Arjan Bokx
--
(replace underscore with dash for email reply)
(vervang underscore door minstreepje voor antwoord per epost. Spam... grr)

<snip>

<snip>
--
Richard H

#include "sig.h"

So often the case. I will have to find the specific reference. I had always
assumed it was common sense, a dangerous assumption.

For now, here is the appropriate excerpt from the comp.lang.c++ FAQ at
http://www.cerfnet.com/~mpcline/c++-faq-lite/how-to-post.html#[5.4]

Key guidelines:

Do not say, "Please respond by e-mail because I don't normally read this
newsgroup". If you don't have enough time for the newsgroup, don't expect
the newsgroup to have enough time for you.
Do not post questions that are answered in the newsgroup's FAQ. That's like
saying your time (to read the FAQ) is more valuable than the time of
hundreds and hundreds of others (to answer your question). Tres uncool. Read
the FAQ first!
Do not cross post your question to a big pile of newsgroups. Post to the
newsgroup (singular) that best fits your question. If you don't get an
answer in the "right" newsgroup, post somewhere else but redirect followups
back to the "right" newsgroup.
Do include a working e-mail address in your signature. If your From: address
is not correct, please notify your system administrator. Until it's fixed,
add a Reply-to: line that gives your correct e-mail address.
--

Paul Lutus
www.arachnoid.com

<snip>

According to the FAQ, Paul, you are in serious violation!

and you have not added a Reply-to: line with a correct one.

Please notify your system administrator at once and flog yourself
senseless with a wet noodle!

</Jack>
--
Do not email me with questions about programming.
Post them to the appropriate newsgroup.
Followups to my posts are welcome.

Paul Lutus
www.arachnoid.com

Just my €0.02. . .

--
Marcus Houlden                                    ICQ: 29654055
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George Washington    |    (800) 222-3333
Abe Lincoln      |  222 333-4444

#include <stdio.h>
#include <stdlib.h>

typedef struct {
   char name[40];
   char nr[20];
   } DATA;

int main(void) {
   DATA *temp,*dataLine = NULL;
   char buf[80];
   unsigned i,record = 0;
   FILE *fp;

   if((fp = fopen("data.txt","r")) == NULL) {
      perror("Unable to open \"data.txt\"");
      exit(EXIT_FAILURE);
      }
   while(fgets(buf,sizeof buf,fp) != NULL) {
      if((temp = realloc(dataLine,(record + 1)*sizeof(*dataLine)))
               == NULL) {
         free(dataLine);
         puts("Unable to allocate memory");
         exit(EXIT_FAILURE);
         }
      dataLine = temp;
      if(sscanf(buf,"%40[^|] | %20[^\n]",dataLine[record].name,
                dataLine[record].nr) != 2) {
         free(dataLine);
         puts("File format error");
         exit(EXIT_FAILURE);
         }
      record++;
      }
   fclose(fp);
   printf("%u records in database\n\n",record);
   for(i = 0;i < record;i++)
      printf("  %-40s %s\n",dataLine[i].name,dataLine[i].nr);
   free(dataLine);
   return 0;
   }
--
Al Bowers
Tampa, FL

http:www.gate.net/~abowers/index.html

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