Path: utzoo!attcan!uunet!cs.utexas.edu!usc!elroy.jpl.nasa.gov!jpl-devvax!lwall
From: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Newsgroups: comp.lang.perl
Subject: Re: Searching fixed-record-length files
Message-ID: <10304@jpl-devvax.JPL.NASA.GOV>
Date: 9 Nov 90 02:01:46 GMT
References: <1990Nov7.233040.8119@cunixf.cc.columbia.edu>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 27

In article <1990Nov7.233040.8119@cunixf.cc.columbia.edu> ben@cunixf.cc.columbia.edu (Ben Fried) writes:
: I've got a file containing a database with a fixed record size of 184
: characters; there is no record separator.  Same for fields within the
: record - they are each a (different) constant size, and are padded with
: blanks out to that size.
: 
: I was trying to think of a way to slurp in the entire file all at once
: (even though it's big - ~8meg), compile the expression to search for,
: and then use format to print out the matching records prettily; however,
: I'm stuck.  The solutions I come up with are all based around records
: and fields all being delimited by some expression, when they're actually
: not.

while (read(DB, $_, 184)) {
    ($once, $upon, $a, $time) = unpack('A20 A30 A50 A84', $_);
    ...
}

This calls fread() internally, so you don't have to worry about short
reads except at eof.  The 'A' specifier in the format template will trim
trailing spaces--use 'a' to keep the spaces.

(If this isn't a one-shot program, you probably want to shove the magic
literals into variables that are set at the top of your program, if not
read out of a file.)

Larry