From: utzoo!decvax!harpo!eagle!mhtsa!alice!rabbit!ark Newsgroups: net.lang.c Title: Re: read/write same file with one open -- Query Article-I.D.: rabbit.1078 Posted: Thu Jan 27 17:48:50 1983 Received: Sun Jan 30 08:07:27 1983 References: burl.53 UNIX System III and, I believe, Berkeley UNIX allow a file to be opened read/write. You say: FILE *f; f = fopen("file", "r+"); (or "w+") The + means that you can read and write. WARNING: If you have been reading and you want to write, or vice versa, you must "switch modes." This can be done by executing lseek or rewind on the file. Normally you will do one of these anyway when changing. (change lseek to fseek in the above line) Note that fseek(f,0L,1) is a no-op, except that after you do it, you can either read or write the file.