Index files

[deewhyren2]

Still have a problem with locating a record in a dynamic array,
overwriting the field with a 'Q' and writing whole array to a file.

On examining the file a 'Q' is written to it but it writes it at the
beginning of the file not in the position denoted by the rec_num.

I've rewritten this part.

Anyone any ideas?


Also the search does find the correct record and where it is in the
master file.

Here's the code snippet:

static RECORD_DATA *search_file(char *key)
{
static RECORD_DATA record;
static RECORD_IDX *idx_list,
*entry_ptr;

register long recs;



FILE *fp_idx;


fp_idx=fopen("A:\STCKMAST.IDX","rb+");


fseek(fp_idx,IDXSIZE,SEEK_END);
recs = (ftell(fp_idx)/IDXSIZE);

/* use malloc(), create alist */
idx_list = (RECORD_IDX *)malloc(recs * IDXSIZE);
/*
{
printf("\nInsufficient memory available. This program will
close.");
pause();
exit(1);
} */

rewind( fp_idx);
fread(idx_list, IDXSIZE * recs,1,fp_idx);
rewind (fp_idx);

/* index = *entry_ptr; */
/* strcpy(index.key, key); */

qsort(idx_list, recs, IDXSIZE, compare);

strcpy(index.key, key);

entry_ptr = (RECORD_IDX *) bsearch(&index, idx_list, recs,
IDXSIZE, compare);




/* new bit */
if(entry_ptr)
{
switch(master.ARec.rec_type)
{
case 'z':
case 'Z': /* delete part num from index file */
index = *entry_ptr;
/* this bit causes Q to be written at the beginning of the file not
in the space found during the search */

strcpy(index.key, "Q");
printf("\n rec num %ld ",entry_ptr->rec_num);

/* entry_ptr->key[0]='Q';*/
/* write whole dynamic array to file */
fwrite(idx_list, (IDXSIZE * recs),1,fp_idx);
pause();
}

[quzah]

The problem is with the way you're opening your file. You really should read up on fopen.

r+ Open for reading and writing. The stream is posi-
tioned at the beginning of the file.

You will want to use a+ instead of r+. This will set the file in append mode.

Quzah.

[deewhyren2]

Thanks for the info, I'm not looking to append the file.

What I'm trying to do is to sort the file once its in the dynamic array and then amend it and then write the array as the new file, so I thought it would just overwrite it. (I could be wrong on this..)

If I append the array to the file then the file will contain similar index info twice..or am I missing something?

Thanks

Andy.

[quzah]

In that case, just read the entire file, and then write it over top of the one that's there.

open the file for reading
read the whole file
close the file
open the file for writing (don't use the +)
write the whole file
close the file

Otherwise, open it as you originally did, read the data, call "rewind()" on the file after you've read it all, and then write the whole thing.

I would still advice reading over the link I provided to see what fopen method would work best for your example.

Quzah.

[deewhyren2]

Thanks for the reply,

am working on it.

Cheers..