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

i open txt file for i-o (+<filename) . when i update a field, the field does not reflect new values? why? i tried closing and opening the file inside the program. still it does not happen. the update happens only when i close the program and come back to dos prompt and run the program again. why? do we have flush facility like 'C' language? what else i should try? ramadurai r

Replies are listed 'Best First'.
Re: update a txt file
by PodMaster (Abbot) on Mar 14, 2004 at 01:15 UTC
    It's because you're doing something wrong, and without code, no one can tell you what. Anyway, Tie::File is nice 
    use Tie::File;
{
   tie my @array, 'Tie::File', 'filename' or die "eek $@ $! $/";
   push @array, scalar localtime;
   unshift @array, scalar gmtime;
}

warn "and the file contains $/";
{
    tie my @array, 'Tie::File', 'filename' or die "eek $@ $! $/";
    print $_,$/ for @array;
}
__END__
$$ perl test
and the file contains
Sun Mar 14 01:19:12 2004
Sat Mar 13 17:19:12 2004

$$ perl test
and the file contains
Sun Mar 14 01:19:14 2004
Sun Mar 14 01:19:12 2004
Sat Mar 13 17:19:12 2004
Sat Mar 13 17:19:14 2004

$$ perl test
and the file contains
Sun Mar 14 01:19:15 2004
Sun Mar 14 01:19:14 2004
Sun Mar 14 01:19:12 2004
Sat Mar 13 17:19:12 2004
Sat Mar 13 17:19:14 2004
Sat Mar 13 17:19:15 2004

    [download]

    MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
    I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
    ** The third rule of perl club is a statement of fact: pod is sexy.

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[d/l]
Re: update a txt file
by pbeckingham (Parson) on Mar 14, 2004 at 01:20 UTC

    Now the following works, and prints "read in 'xxx'". Given the file io.txt: 

      onetwothreefour

    [download]
    and the following code: 
      #! /usr/bin/perl -w
  use strict;

  if (open FILE, '+<io.txt')
  {
    seek FILE, 3, 0;
    print FILE 'xxx';

    seek FILE, 3, 0;
    my $input = '';
    sysread FILE, $input, 3;
    print "read in '$input'\n";

    close FILE;
  }

    [download]
    But you really ought to have provided the misbehaving code.

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[d/l]
[select]
Re: update a txt file
by Anonymous Monk on Mar 14, 2004 at 03:56 UTC
    You should be passing seek 0 (zero) as the second argument, not 5. You are missing a semi-colon after line 36, and there is no such module Term::ReadALine. My answersmake about as much sense as your question.
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