use Fcntl ':seek'; # Take the record at the current position of $fh, # and replace it with $rec if possible sub modify { my ($fh, $rec) = @_; my $pos = tell $fh; chomp(my $oldrec = <$fh>); seek $fh, $pos, SEEK_SET; if (length $oldrec == length $rec) { # easy case print $fh $rec; } elsif (length $rec < length $oldrec) { my $shortfall = length($oldrec) - length($rec) ; my $fill = "0円" x ($shortfall-1); print $fh $rec, "\n", $fill; } else { # New record is too big my $fill = "0円" x length($oldrec); print $fh $fill; seek $fh, 0, SEEK_END; # New record goes at the end print $fh $rec, "\n"; } } # Locate the first record in the file that starts with '$key' # Leave the filehandle positioned at its start # Return the record, or undef if no such record sub find { my ($fh, $key) = @_; seek $fh, 0, SEEK_SET; my $pos = 0; while (<$fh>) { chomp; next unless /[^0円]/; if (index($_, $key) == 0) { seek $fh, $pos, SEEK_SET; return $_; } $pos = tell $fh; } return; } open F, "+<", "MIP" or die $!; ($u, $p) = split /:/, find(\*F, 'gnat'); modify(\*F, "torkington:$p"); ($u, $p) = split /:/, find(\*F, 'tchrist'); modify(\*F, "tom:$p"); ($u, $p) = split /:/, find(\*F, 'lenhard'); warn "$u = $p\n";