tigervamp has asked for the wisdom of the Perl Monks concerning the following question:

The problem is that I am trying to read a fixed length of test from a file, say the first 200 characters, I tried the following: 
$count=200;
$/ = \$count;
open(FILE1,"a.txt");
$record=<FILE1>;
close(FILE1);
print $record;

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and the following: 
$/ = \2000;
open(FILE1,"a.txt");
$record=<FILE1>;
close(FILE1);
print $record;

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but I keep getting the whole file, not a record. I tried this for Linux and Windows. What am I doing wrong?

Thanks,

tigervamp

Replies are listed 'Best First'.
(tye)Re: Reading fixed length records
by tye (Sage) on May 25, 2001 at 18:27 UTC

    What am I doing wrong?

    Trying to use this feature on a version of Perl that doesn't support it.

    Update: I'm not sure why, but I decided to expand on this. If you have Perl prior to version 5.6, then setting $/ to \20 will cause <> to read until it finds the string "SCALAR(0xbadf00d)" (approximately).

            - tye (but my friends call me "Tye")
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[d/l]
Re: Reading fixed length records
by clintp (Curate) on May 25, 2001 at 17:16 UTC 
    $/=\10;
open(F, "foo.txt") || die;
$rec=<F>;
print length $rec, "\n";
close(F);

    [download]
    Always results in 10, for files of at least 10 bytes. Are you sure your file is 2K long? That's a mighty-big record.
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[d/l]
      Using your exact code, and a file of 52164 bytes, the beginning of which is:

      This is a test.
      This is a test.
      This is a test.
      This is a test.This is a test.
      This is a test.
      This is a test.
      ...

      I always get 52164, not 10.

      tigervamp

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Re: Reading fixed length records
by Trimbach (Curate) on May 25, 2001 at 17:15 UTC
[reply]
      I know that I could use pack/unpack, but I would like to know what I am doing wrong in this case, since there is a very similiar example in "Programming Perl" (pg. 666) that claims to work as described.

      tigervamp

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Re: Reading fixed length records
by Vynce (Friar) on May 25, 2001 at 17:22 UTC
    What am I doing wrong?

    using <> instead of read.

    (Golf score: 24)

[reply]

      Whilst I'd probably use read in this case, there's no reason why to can't use <>. Setting $/ to a reference to a number will set the number of bytes returned each time.

      --
      <http://www.dave.org.uk>

      "Perl makes the fun jobs fun
      and the boring jobs bearable" - me

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Re: Reading fixed length records
by princepawn (Parson) on May 25, 2001 at 22:59 UTC
[reply]

      Is it just me, or do the terms "Parse" and "FixedLength" seem to be at odds with each other? ;)

              - tye (but my friends call me "Tye")
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