NAME
Encode::Escape - Perl extension for Encodings of various escape
sequences
SYNOPSIS
use Encode::Escape;
$escaped_ascii = "Perl\\tPathologically Eclectic Rubbish Lister\\n";
$ascii = decode 'ascii-escape', $escaped_ascii;
# Now, $ascii is equivalent to
# double quote string "Perl\tPathologically Eclectic Rubbish Lister\n"
$escaped_unicode = "Perl \\x{041F}\\x{0435}\\x{0440}\\x{043B} \\x{D384}"
$string = decode 'unicode-escape', $escaped_unicode;
# Now, $string is equvialent to
# double quote string "Perl \x{041F}\x{0435}\x{0440}\x{043B} \x{D384}"
It may looks non-sense. Here's another case.
If you have a text data file 'ascii-escape.txt'. It contains a line:
Perl\tPathologically Eclectic Rubbish Lister\n
And you want to use it as if it were a normal double quote string in
source code. Try this:
open(FILE, 'ascii-escape.txt');
while(<FILE>) {
chomp;
print decode 'ascii-escape', $_;
}
DESCRIPTION
Encode::Escape module is a wrapper class for encodings of escape
sequences.
It is NOT for an escape-based encoding (eg. ISO-2022-JP). It is for
encoding/decoding escape sequences, generally used in source codes.
Many programming languages, markup languages, and typesetting languages
provide methods for encoding special (or functional) characters and
non-keyboard symbols in the form of escape sequence. That's what I
concern.
Yes, you're right. There already exist many modules. See String::Escape,
Unicode::Escape, TeX::Encode, HTML::Mason::Escape,
Template::Plugin::XML::Escape, URI::Escape, etc.
But for some reason I need to do it in a different way. There is more
than one way to do it! After that, I asked myself if this module is
useful. May be not except for me. At this time, Zhuangzi reminds me,
""The useless has its use"".
ASCII
See Encode::Escape::ASCII
Unicode
See Encode::Escape::Unicode
ESCAPE SEQUENCES
Character Escape Codes
ASCII defines 128 characters: 33 non-printing control characters (0x00
-- 0x1f, 0x7f) and 95 printable characters (0x20 -- 0x7e).
Character Escape Codes in C programming language provide a method to
express control characters, using only printable ones. These are
accepted by Perl and many other languages.
CEC HEX Description
--- ---- --------------
\0 00 Null character
\a 07 Bell
\b 08 Backspace
\t 09 Horizontal Tab
\n 0a Line feed
\v 0b Vertical Tab
\f 0c Form feed
\r 0d Carriage return
Programming languages provide escape sequences for printable characters,
which have significant meaning in that language. Otherwise, it would be
harder to print them literally.
ESC HEX Description
--- ---- ---------------
\" 22 double quote
\\ 52 backslash
Refer to ASCII, Escape character, Escape sequence at
<http://en.wikipedia.org>, for more details.
Perl Escape Sequences
Perl use backslash as an escape character.
These work in normal strings and regular expressions except \b.
ESC Description
--- --------------------------
\a Alarm (beep)
\b Backspace
\e Escape
\f Formfeed
\n Newline
\r Carriage return
\t Tab
\037 Any octal ASCII value
\x7f Any hexadecimal ASCII value
\x{263a} A wide hexadecimal value
\cx Control-x
\N{name} name is a name for the Unicode character (use charnames)
The following escape sequences are available in constructs that
interpolate.
\l Lowercase next character
\u Titlecase next character
\L Lowercase until \E
\U Uppercase until \E
\E End case modification
In regular expresssions:
\b An assetion, not backspace, except in a character class
\Q Disable pattern metacharacters until \E
Unlike C and other languages, Perl has no \v escape sequence for the
vertical tab (VT - ASCII 11).
For constructs that do interpolate, variable begining with "$" or "@"
are interpolated.
\$ Dollar Sign
\@ Ampersand
\" Print double quotes
\ Escape next character if know otherwise print
See perlreref, perlop
Python Escape Sequences
\newline Ignored
\\ Backslash (\)
\' Single quote (')
\" Double quote (")
\a ASCII Bell (BEL)
\b ASCII Backspace (BA)
\f ASCII Formfeed (FF)
\n ASCII Linefeed (LF)
\N{name} Character named 'name' in the Unicode database
\r ASCII Carriage Return (CR)
\t ASCII Horizontal Tab (TAB)
\uxxxx Character with 16-bit hex value xxxx (Unicode only)
\Uxxxxxxxx Character with 32-bit hex value xxxxxxxx (Unicode only)
\v ASCII Vertical Tab (VT)
\ooo Character with octal value ooo
\xhh Character with hex value hh
See <http://docs.python.org/ref/strings.html>
Unicode escape sequences in the form of "\u"*xxxx* are used in Java,
Python, C#, JavaScript. Unicode::Escape module implements it.
LaTeX Escapes
TeX::Encode implements encodings of LaTeX escapes. It converts (encodes)
utf8 string to LaTeX escapes.
HTML Escapes
See HTML::Mason::Escapes
SEE ALSO
The useless has its use
Hui Tzu said to Chuang Tzu, "Your words are useless!"
Chuang Tzu said, "A man has to understand the useless before you can
talk to him about the useful. The earth is certainly vast and broad,
though a man uses no more of it than the area he puts his feet on. If,
however, you were to dig away all the earth from around his feet until
you reached the Yellow Springs, then would the man still be able to make
use of it?"
"No, it would be useless," said Hui Tzu.
"It is obvious, then," said Chuang Tzu, "that the useless has its use."
AUTHOR
You Hyun Jo, <you at cpan dot org>
ACKNOWLEDGEMENTS
Matthew Simon Cavlletto for String::Escape. It worked as good reference
when writing the first working version of Encode::Escape::ASCII.
COPYRIGHT AND LICENSE
Copyright (C) 2007 by You Hyun Jo
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself, either Perl version 5.8.8 or, at
your option, any later version of Perl 5 you may have available.