if ( $line =~ /NEWTABLE/) {
         print "b4 seek $line\n";
         print "len :$length:\n";
         seek(FH, (0 - length($line)), SEEK_CUR);
         chomp($line=<FH>);
         print "--> $line\n";
         exit;
       }
[download]

The above coed still prints the next line after using seek. am I missing something there in the seek function ?

The negative seek may not work in windows... not sure. It definitely does work on my linux box though. I don't have any windows handy or I'd test it. I did notice you didn't use "or die $!. " Most likely it would return an error result on your platform.

use strict;
use Fcntl qw(:seek);

open my $in, "filename" or die $!;

my $line = <$in>;
print "$line\n";

seek $in, (0 - length $line), SEEK_CUR or die $!;

$line = <$in>;
print "$line\n";

close $in;
[download]

It should either work or complain...

-Paul

Hi

if ( $line =~ /NEWTABLE/) {
   seek(FH, (0 - length($line)+tell(FH)), SEEK_CUR);
   $line = <FH>;
   chomp($line);
   print "LINE AFTER SEEK :$line:\n"
}
[download]

Output :-

"LINE AFTER SEEK :EWTABLE:\n"
[download]

why I am missing 'N' after the seek ?
"Keep pouring your ideas"

There's definitely someting screwy with using a negative, relative seek (on Win32). To back up over a line consisting of 8 chars + NL, requires seeking back -6.

I'd expect to have to seek back more than the line length, not less to account for the newline?

#! perl -slw
use strict;

while( <DATA> ) {
    chomp;
    print;
    if( /the line/ ) {
        my $backup = -length() + 2;
        print "Backing up $backup places";
        seek DATA, $backup, 1;
        chomp( $_ = <DATA> );
        print "?$_?";
    }
}

=output
c:\test>junk
junk
junk
more junk
the line
Backing up -6 places
?the line?
other junk
yet more junk
=cut
__DATA__
junk
junk
more junk
the line
other junk
yet more junk
[download]

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

seek(FH, (0 - length($line)+tell(FH)), SEEK_CUR);

You are seeking too far back. You're seeking back the length of the string plus the byte-number of your current position...

If you wish to use tell() to record the old position before your read, then you'd use: seek(FH, $old_position, SEEK_SET); instead.

-Paul