Add text to beginning every line

[Chris Charley]

Hi

Hope someone can help with this. I used to be able to do it, but now have
forgotten. I want to prepend some text to every line in a file. The program
below:

#!/usr/bin/perl
# prepend.pl - adds line number to beginning of every line in a file
use strict;
use warnings;

while (<>) {
s/^/Line: $. /;
}

Then, on the command line I type: perl prepend.pl somefile.txt, but
somefile.txt does not have the changes(Line: <linenumber>).

Thanks for any explanation you may offer.

Chris

[Chris Charley]

"Chris Charley" <charleyNOSPAM@pulsenetNOSPAM.com> wrote in message news:...
[snip]

> while (<>) {
> s/^/Line: $. /;
> }

Should be (works correctly):

while (<>) {
s/^/Line: $. /;
print;
}

Then the command could be: perl prepend.pl somefile.txt > somefile.new
which would correctly print to the 'new' file the somefile.txt file with the
line numbers prepended.

Chris

[Tim Johnson]

You're reading in the file, but not changing it. You're only changing it in
memory. Check out the responses to the other post called "make changes to a
file, then reading in those changes"

-----Original Message-----
From: Chris Charley [mailto:charleyNOSPAM@pulsenetNOSPAM.com]
Sent: Monday, October 06, 2003 11:20 AM
To: [email]beginners@perl.org[/email]
Subject: Add text to beginning every line


Hi

Hope someone can help with this. I used to be able to do it, but now have
forgotten. I want to prepend some text to every line in a file. The program
below:

#!/usr/bin/perl
# prepend.pl - adds line number to beginning of every line in a file use
strict; use warnings;

while (<>) {
s/^/Line: $. /;
}

Then, on the command line I type: perl prepend.pl somefile.txt, but
somefile.txt does not have the changes(Line: <linenumber>).

Thanks for any explanation you may offer.

Chris



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[Thomas bätzler]

Hi,

Chris Charley <charleyNOSPAM@pulsenetNOSPAM.com> wrote:

> Should be (works correctly):
>
> while (<>) {
> s/^/Line: $. /;
> print;
> }
>
> Then the command could be: perl prepend.pl somefile.txt >
> somefile.new
> which would correctly print to the 'new' file the
> somefile.txt file with the line numbers prepended.

I would even suggest

perl -i.bak -pe 's/^/Line $.: /' <filenames>

This will do the replacement on one or more files
whose names oyu give on the command line. Perl
will then create backup files with the .bak extension
and modify the original files.

HTH,
Thomas

[Sudarshan Raghavan]

Chris Charley wrote:

> "Chris Charley" <charleyNOSPAM@pulsenetNOSPAM.com> wrote in message news:...
> [snip]

> > while (<>) {
> > s/^/Line: $. /;
> > }

>
> Should be (works correctly):
>
> while (<>) {
> s/^/Line: $. /;

You don't need a regular expression to do this. This should suffice
$_ = "Line: $. $_";

I hope you are aware of the fact that $. does not loop back to 0 when you pass
multiple files in the argument list.
When the call is 'perl prepend.pl somefile1.txt somefile2.txt', $. will not
loopback to 0 when the processing of 'somefile1.txt' finishes and
'somefile2.txt' starts.
perldoc perlop #Search for 'null filehandle'

>
> print;
> }
>
> Then the command could be: perl prepend.pl somefile.txt > somefile.new
> which would correctly print to the 'new' file the somefile.txt file with the
> line numbers prepended.
>
> Chris
>
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> To unsubscribe, e-mail: [email]beginners-unsubscribe@perl.org[/email]
> For additional commands, e-mail: [email]beginners-help@perl.org[/email]

[Tore Aursand]

On Mon, 06 Oct 2003 14:20:05 -0400, Chris Charley wrote:

> Then, on the command line I type: perl prepend.pl somefile.txt, but
> somefile.txt does not have the changes(Line: <linenumber>).

Try writing 'perl prepend.pl somefile.txt > newfile.txt' instead.


--
Tore Aursand <tore@aursand.no>