Re: Putting a line in a specific place in a file

samasama wrote:
anno4000@xxxxxxxxxxxxxxxxxxxxxx wrote:
samasama <bryan@xxxxxxxxxxxxxx> wrote in comp.lang.perl.misc:

[positioning a file handle]

This finds the lines correctly but if I try to print after $gpg_line,
the line below gets fubar.
I know I could use Tie::File, but i really want to understand what's
going on and how to insert my line after $gpg_line correctly.
Well, you can't.

A file is really a sequence of bytes, no more, no less. You can
append to the end of a file, but writing anywhere else implies
overwriting what's already there.


Duh... Yeah I feel dumb : P I don't know why I thought I could just
print the line.

Pity we can no longer refer to the FAQ for this question.

Perlfaq5 "How do I change one line in a file/delete a line..." used to
explain this problem in detail. These days it just refers to Tie::File,
another tool that makes files look like a sequence (a Perl array) of lines.

Yeah, Tie::File is great, but I needed to learn the steps in writing my
own parser, for future projects.

While, I've figured out what I needed to do and I'll paste the last of
the code below... I still don't understand what if ( ( $. == $base_line
.. /gpgkey\=/i ) =~ /E/ ) { translates too.
It looks like $. == $base_line go down using .. until we hit gpgkey,
and I have no idea what the /E/ means. I'd really like to understand
that.

Perhaps a demonstration may help:

$ seq 10 18 | perl -lne' my $x = 3 .. /16/; print "Line Number: $. Contents:
$_ Flip-flop: $x" '
Line Number: 1 Contents: 10 Flip-flop:
Line Number: 2 Contents: 11 Flip-flop:
Line Number: 3 Contents: 12 Flip-flop: 1
Line Number: 4 Contents: 13 Flip-flop: 2
Line Number: 5 Contents: 14 Flip-flop: 3
Line Number: 6 Contents: 15 Flip-flop: 4
Line Number: 7 Contents: 16 Flip-flop: 5E0
Line Number: 8 Contents: 17 Flip-flop:
Line Number: 9 Contents: 18 Flip-flop:



John
--
Perl isn't a toolbox, but a small machine shop where you can special-order
certain sorts of tools at low cost and in short order. -- Larry Wall
.

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