Updating a binary file

[DerPflug]

Can anyone offer any practical steps in updating and deleting records in a binary file? I'm writing a simple app (console application) that updates, deletes, and inserts records in a binary inventory file. All of the records are entered as structs.
My main conundrum is what the series of events is in each of the functions.

update: How can I allow the user to pull up the requested file and be able to edit it while in the window, meaning jump from field to field and then save it?

delete: Deletes are accomplished with a logical delete, i.e. a delete flag.

Thanks for any insight.

 

[rbobbitt]

If the records aren't sorted, you could iteratively search through the file, record by record, until you find the proper record to update.

while (fread(&foo,sizeof foo,1,fp)==1) {
/* Compare foo to the search
* record. Exit loop if it matches. */
}

Once you've found it, you'll need to fseek() back one record (since the file pointer will have been advanced to the next record)

fseek(fp,-(sizeof foo),SEEK_CUR);

And then use fwrite() to overwrite the record with the updated one.

fwrite(&new_rec,sizeof new_rec,1,fp);

To delete a record, you would use the same search function, except you would write a "dummy" record in the appropriate place in the file with the delete flag set.

If you've sorted the records in the file, you could do a binary search with fseek().
Russ
bobbitts@hotmail.com

http://home.earthlink.net/~bobbitts

 

[DerPflug]

Many thanks! I understand completely.