Perl beginner: How can I find/replace ascii characters in a file?

Use the \x## notation:

perl -pi~ -e 's/\x00/*/g' test.txt 

To replace each "special" character with its code in brackets, use the /e option:

perl -pi~ -e 's/([\x0-\x09\x11-\x1f])/"[" . ord($1) . "]"/eg' test.txt 

Wow, thank you very much. I learned that it wasn't as easy as I assumed. Wow, Perl is truly very complex ;-)

Here is, what I came up with. I hope this will help someone.

BTW: If you have any chance to know if this will also work on Windows Perl, please let me know.

Thanks again,

Gary

#!/usr/bin/perl use strict; use warnings; my $infile = '/Users/gc/Desktop/a.bin'; my $outfile = '/Users/gc/Desktop/b.txt'; # in and out can be the same file; file will be overwritten when it already exists my $data = read_file($infile); # 1st batch $data =~ s/0\x01J[\x00-\x19]/\x09AnythingYouWant\x09/g; $data =~ s/0\x00[\x00-\x19]/\x09AnythingYouWant\x09/g; # 2nd batch $data =~ s/\r/\x06/g; # CR into \x06 $data =~ s/\n/\x06/g; # LF into \x06 $data =~ s/\r\n/\x06/g; # CR LF into \x06 # … write_file($outfile, $data); exit; sub read_file { my ($infile) = @_; open my $in, '<', $infile or die "Could not open '$infile' for reading $!"; local $/ = undef; my $all = <$in>; close $in; return $all; } sub write_file { my ($outfile, $content) = @_; open my $out, '>', $outfile or die "Could not open '$outfile' for writing $!";; print $out $content; close $out; return; } 

Although it's a bit weird to do string replaces on a binary file, here's how to do it with your txt file:

use strict; use warnings; use Tie::File; my @file; tie @file, 'Tie::File', 'test.txt' or die $!; foreach (@file) { # your regexes go here s/abc/123/g; s/\0x49/*/g; } untie @file; 

The Tie::File module (from the Perl core) allows you to access the lines of the file through an array. Changes will be saved to the file immediately. In the foreach loop, the file is processed line by line. The lines go into $_, which we cannot see. The regex operations are by default also applied to $_, so there's no need to write it down.

However, I believe you are going about this the wrong way. In most cases, you will not be able to just read the file line by line. Refer to perlfaq as a starting point. Dealing with binary is somewhat more tricky than just text processing I'm afraid.