In vi you can type :set list and all tabs will shown as ^I and the end of line will be shown as $. Type :set nolist to go back to a normal display.

Perl Training in the UK <http://www.iterative-software.com>

I just add that in vim there is also :help 'listchars' to give you further control on what to display for a tab, eol and trailing spaces.

-- Hofmator

    local $\ = '';
    my $filename = "/mydir/myfile";
    open FILE, "<$filename"
        or die "Cannot open $filename for reading\n";
    my $file = <FILE>;
    close FILE;

    $file =~ s/\t/\\t/g;

    open FILE, ">$outfilename"
        or die "Cannot open $outfilename for writing\n";
    print FILE $file;
    close FILE;
[download]

The reason to use s/// instead of tr/// is that you are replacing in a 1:n relationship and not the 1:1 that tr requires.

------
/me wants to be the brightest bulb in the chandelier!

Vote paco for President!

or in one line: perl -pe 's/\t/\\t/g' infile > outfile to allow for more substitutions consider a hash like

my %mapping = ( # or whatever you like to display
  "\t" => '\t',
  "\n" => '\n',
  " "  => '_',
);

my $pattern = qr/([@{[join '', keys %mapping]}])/;

while ( <> ) {
  s/$pattern/$mapping{$1}/g;
  print "$_\n"; # you still want to start a new line
}
[download]

This works fine as long as your keys are only characters, otherwise you have to use an alternation instead of a character class.

-- Hofmator

You might need to load the library (either add "(load-library "whitespace-mode")" to your .emacs, or if you just want it once, say "M-x load-library RET whitespace-mode RET"). Then, to activate it, hit "M-x whitespace-mode RET" and watch your spaces and tabs light up in different colours.

Note to the unenlightened: you never really type in these long sequences at (X)Emacs: you use TAB or SPACE to get completion.

A good way to show your mom might be using a hex editor, so that you can see the actual bytes in the file. In emacs, that would done by using "M-x hexl-mode" when viewing the file.

Christian Lemburg
Brainbench MVP for Perl
http://www.brainbench.com

This is a nice way to map it out and preserve the spatial relationships of the text. Tabs are changed to ' -> ' and spaces to dots '·' (chr 183 ASCII). This is how my editor displays them when I select the display all chars option. chr 182 ASCII is that funny backwards P symbol ¶ used for newlines. We use the octal naming convention for these chars for convenience. chr 0266 = '¶' and chr 0267 = '·'

In the unlikely event these special chars are included in the text to be processed we hex encode them using the standard URL encoding convention of a % followed by two hex digits. We can then remove the URL encoding to regenerate our original text.

sub show {
    my @data = @_;
    for (@data) {
        s/(\266|\267)/sprintf"%%%02X",ord $1/egm;
        s/ /chr(0267)/egm;
        s/\t/ -> /gm;
        s/\n/chr(0266)."\n"/egm;
    }
  return wantarray ? @data : join'',@data;
}

sub hide {
    my @data = @_;
    for (@data) {
        s/ -> /\t/gm;
        s/\266//gm;
        s/\267/ /gm;
        s/%([0-9a-f][0-9a-f])/chr hex $1/eigm;
    }
  return wantarray ? @data : join'',@data;
}

@data = (<DATA>)[0..7];

print "Original data, including specials\n\n";
print @data;

print "\n\nShow invisible chars in data\n\n";
print show(@data);

print "\n\nHide and show data - should not change\n\n";
print hide(show(@data));

__DATA__
    tab
    4 spaces, trailing tab    
        tab and 4 spaces
        
····4·spaces,·trailing·tab -> ¶
 -> ····tab·and·4·spaces¶
 ->  -> ¶
¶
[download]

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

These are available on CPAN and on ActiveState PPM:

#!perl -w

use strict;

my $buf = "Look, Ma:\nfoo\tbar\tsee those tabs?\nFOO   BAR  look here 
+- no tabs, just spaces.\n";
print "$buf\n";

use Data::HexDump;
print "HexDump:\n", HexDump "$buf";

use Data::Hexdumper;
print "Hexdumper:\n", Data::Hexdumper::Hexdump(data => $buf);
[download]

Rudif