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From: gordon@osiris.cso.uiuc.edu (John Gordon)
Newsgroups: comp.lang.c
Subject: Re: Random Access files
Message-ID: <1990Nov20.014554.17886@ux1.cso.uiuc.edu>
Date: 20 Nov 90 01:45:54 GMT
References: <90322.032603TRM900@psuvm.psu.edu>
Sender: news@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 24

Tony R. Marasco <TRM900@psuvm.psu.edu> writes:

>Hello.  I am trying to use random access files and have run into some
>problems...

>I am using _fopen_ with a "w+b" parameter to create the file (if it doesn't
>exist).  If it exists, I use "r+b".  Otherwise it seems to erase the file
>like PASCAL's _rewrite_.  How am I doing so far??

	Opening a file in "w" mode is supposed to destroy existing files.  If
you don't want to do this, open in "a" mode.

>I am also using _fseek_ to position the file pointer (recnum*size of struct)
>with SEEK_SET.  I do this before each _fread_ & _fwrite_.  The program
>seems to "lose" a few bytes at the beginning of each _fread_.

	The first record number should be at recnum 0.  Are you starting at
recnum 1?


>What is more astounding is I can write a record that doesn't exist, but
>I can't update a record that already exists.

	I think that opening in "a" might work.