Search & replace string in file : perl, replace, file, string, search

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07.25.2003 at 10:37AM PDT, ID: 20690580

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7.4

Search & replace string in file

Zone: Perl Programming Language

Tags: perl, replace, file, string, search

I want to pre-configure a software package that people download from a webserver. For this I'd like to preset some strings inside a binairy application file.

Basically what I need is a Perl procedure that will load the binairy file, look for a specific string, replace it with another one of the same length, and then save the file.

Doesn't sound too complicted, but I'm not a Perl expert, so that's why I am asking here :)

Thanks in advance,

P.

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Question Stats

Zone: Programming

Question Asked By: BorlandDelphi

Solution Provided By: holli

Participating Experts: 2

Solution Grade: A

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07.25.2003 at 11:28AM PDT, ID: 9006899

Rank: Master

holli:

you can put the following into a batch-file:

@echo off
perl -0ni.old -e "s/^(.{offset})searchtext/\1replacement/;print;" %1
rem remove this to keep the original file
del %1.old
goto end

:error
echo Usage foo.bat [filename]
:end

change offset, searchtext and replacement to your needs.

07.25.2003 at 11:37AM PDT, ID: 9006988

BorlandDelphi:

What I would like is just a Perl script like Replace.pl with this function in it because it also has to read the replacement text from another file.

In other words what would a function in that script look like?
Also, what is the offset variable for, can you explain just a little? :)

Thanks,

P.

07.25.2003 at 11:44AM PDT, ID: 9007056

Rank: Master

holli:

just realized that binary files have some difficulties under windows, and that there is a small bug in the above code.
the following is better:

perl -0777 -ni.old -e "BEGIN { binmode (STDIN);binmode (STDOUT) }" -e "s/^(.{68})DEU/\1deu/;print;" command.com

(07.. is zero-seven, not o-seven)

07.25.2003 at 11:48AM PDT, ID: 9007080

BorlandDelphi:

It's a Unix web server, so I don't think I'll have any Windoze problems :)

07.25.2003 at 11:49AM PDT, ID: 9007089

Rank: Master

holli:

>>What I would like is just a Perl script like Replace.pl with this function in it because it also has to read the replacement text from another file.
fine.

In other words what would a function in that script look like?
Also, what is the offset variable for, can you explain just a little? :)
the offset is the position of the searchtext (here starting from the begining of the file), simply because binaries can contain anything.
if you cannot tell the offset, we have to find another regex that ensures that only the wanted part is replaced.

07.25.2003 at 11:49AM PDT, ID: 9007098

Rank: Master

holli:

just an assumption because of your nickname :-)

07.25.2003 at 12:16PM PDT, ID: 9007323

BorlandDelphi:

Delphi is for PC programming... I like my servers to be Unix though.

I'm still confused though....

This is what I would like...

$infile = '/datadir/infile.bin';
$outfile = '/datadir/outfile.bin';
$orgtext = 'hello world';
$newtext = 'HELLO WORLD';

sub create_file {
load the file
change the text
save the file
}

I don not understand the -0ni.old -e "s/^(.{offset})searchtext/\1replacement/;print;" %1 line else I could put it in the function... can you explain it to me or show me how to convert it into the function? Perl for dummies is just not cutting it :)

Thanks!

07.25.2003 at 01:54PM PDT, ID: 9008106

Rank: Master

holli:

well, then.

$infile = '/datadir/infile.bin';
$outfile = '/datadir/outfile.bin';
$orgtext = 'hello world';
$newtext = 'HELLO WORLD';

undef $/; #slurp mode, read files in a whole

open IN, $infile or die $!;
$intext = <IN>;
close IN;

$intext = s/$orgtext/$newtext/ms;

open OUT, ">$outfile" or die $!;
print OUT $intext;
close OUT;

Accepted Solution

07.25.2003 at 02:46PM PDT, ID: 9008410

BorlandDelphi:

Cool... after going through my Perl for dummies book I came up with

$count = ($data =~ s/$orgtext/$newtext/g);

I'm sure yours is better though :)

Thanks for all your help!

07.26.2003 at 11:04AM PDT, ID: 9011642

Rank: Master

holli:

not better. different.
the was a typo in mine, sorry. it should have been:

$intext =~ s/$orgtext/$newtext/ms;

the ms is for coping correctly with newlines (that can easily appear in a binary).

$count = ($data =~ s/$orgtext/$newtext/g);

replaces ALL occurrences of orgtext with newtext and places the number of occurences in $count.

03.03.2004 at 07:03PM PST, ID: 10510762

melindaj:

Hello
The code above also worked for me but having problem with the search string if has (NBL) for example if $orgtext = 'hello world (NBL)';
What I need to do ?

03.03.2004 at 11:37PM PST, ID: 10511900

Rank: Master

holli:

this is because the brackets () are special chars in the regexp. you need to escape them.

$orgtext = 'hello world $NBL$';

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