oracular (3) String::Escape.3pm.gz
NAME
String::Escape - Backslash escapes, quoted phrase, word elision, etc.
SYNOPSIS
This module provides a flexible calling interface to some frequently-performed string conversion
functions, including applying and removing backslash escapes like \n and \t, wrapping and removing
double-quotes, and truncating to fit within a desired length.
use String::Escape qw( printable unprintable );
# Convert control, high-bit chars to \n or \xxx escapes
$output = printable($value);
# Convert escape sequences back to original chars
$value = unprintable($input);
use String::Escape qw( elide );
# Shorten strings to fit, if necessary
foreach (@_) { print elide( $_, 79 ) . "\n"; }
use String::Escape qw( string2list list2string );
# Pack and unpack simple lists by quoting each item
$list = list2string( @list );
@list = string2list( $list );
use String::Escape qw( escape );
# Defer selection of escaping routines until runtime
$escape_name = $use_quotes ? 'qprintable' : 'printable';
@escaped = escape($escape_name, @values);
INTERFACE
All of the public functions described below are available as optional exports.
You can either import the specific functions you want, or import only the "escape()" function and pass it
the names of the functions to invoke.
Quoting
Each of these functions takes a single simple scalar argument and returns its escaped (or unescaped)
equivalent.
quote($value) : $escaped
Add double quote characters to each end of the string.
unquote($value) : $escaped
If the string both begins and ends with double quote characters, they are removed, otherwise the
string is returned unchanged.
quote_non_words($value) : $escaped
As above, but only quotes empty, punctuated, and multiword values; simple values consisting of
alphanumerics without special characters are not quoted.
singlequote($value) : $escaped
Add single quote characters to each end of the string.
unsinglequote($value) : $escaped
If the string both begins and ends with single quote characters, they are removed, otherwise the
string is returned unchanged.
Backslash Escaping Functions
Each of these functions takes a single simple scalar argument and returns its escaped (or unescaped)
equivalent.
These functions recognize common whitespace sequences "\r", "\n", and "\t", as well as hex escapes "\x4F"
and ocatal "\020".
When escaping, alphanumeric characters and most punctuation is passed through unchanged; only the return,
newline, tab, backslash, dollar, at sign and unprintable control and high-bit characters are escaped.
backslash($value) : $escaped
Converts special characters to their backslash-escaped equivalents.
unbackslash($value) : $escaped
Converts backslash escape sequences in a string back to their original characters.
qqbackslash($value) : $escaped
Converts special characters to their backslash-escaped equivalents and then wraps the results with
double quotes.
unqqbackslash($value) : $escaped
Strips surrounding double quotes then converts backslash escape sequences back to their original
characters.
Here are a few examples:
•
print backslash( "\tNow is the time\nfor all good folks\n" );
\tNow is the time\nfor all good folks\n
•
print unbackslash( '\\tNow is the time\\nfor all good folks\\n' );
Now is the time
for all good folks
Legacy Backslash Functions
In addition to the four functions listed above, there is a corresponding set which use a slightly
different set of escape sequences.
These functions do not support as many escape sequences and use a non-standard format for hex escapes. In
general, the above "backslash()" functions are recommended, while these functions are retained for legacy
compatibility purposes.
printable($value) : $escaped
Converts return, newline, tab, backslash and unprintable characters to their backslash-escaped
equivalents.
unprintable($value) : $escaped
Converts backslash escape sequences in a string back to their original value.
qprintable($value) : $escaped
Converts special characters to their backslash-escaped equivalents and then wraps the results with
double quotes.
(Note that this is not MIME quoted-printable encoding.)
unqprintable($value) : $escaped
Strips surrounding double quotes then converts backslash escape sequences back to their original
value.
Other Backslash Functions
In addition to the functions listed above, there is also one function that mirrors the behavior of Perl's
built-in "quotemeta()" function.
unquotemeta($value) : $escaped
Strips out backslashes before any character.
Elision Function
This function extracts the leading portion of a provided string and appends ellipsis if it's longer than
the desired maximum excerpt length.
elide($string) : $elided_string
elide($string, $length) : $elided_string
elide($string, $length, $word_boundary_strictness) : $elided_string
elide($string, $length, $word_boundary_strictness, $elipses) : $elided_string
Return a single-quoted, shortened version of the string, with ellipsis.
If the original string is shorter than $length, it is returned unchanged. At most $length characters
are returned; if called with a single argument, $length defaults to $DefaultLength.
Up to $word_boundary_strictness additional characters may be ommited in order to make the elided
portion end on a word boundary; you can pass 0 to ignore word boundaries. If not provided,
$word_boundary_strictness defaults to $DefaultStrictness.
$Elipses
The string of characters used to indicate the end of the excerpt. Initialized to '...'.
$DefaultLength
The default target excerpt length, used when the elide function is called with a single argument.
Initialized to 60.
$DefaultStrictness
The default word-boundary flexibility, used when the elide function is called without the third
argument. Initialized to 10.
Here are a few examples:
•
$string = 'foo bar baz this that the other';
print elide( $string, 12 );
# foo bar...
print elide( $string, 12, 0 );
# foo bar b...
print elide( $string, 100 );
# foo bar baz this that the other
escape()
These functions provide for the registration of string-escape specification names and corresponding
functions, and then allow the invocation of one or several of these functions on one or several source
string values.
escape($escapes, $value) : $escaped_value
escape($escapes, @values) : @escaped_values
Returns an altered copy of the provided values by looking up the escapes string in a registry of
string-modification functions.
If called in a scalar context, operates on the single value passed in; if called in a list contact,
operates identically on each of the provided values.
Space-separated compound specifications like 'quoted uppercase' are expanded to a list of functions
to be applied in order.
Valid escape specifications are:
one of the keys defined in %Escapes
The coresponding specification will be looked up and used.
a sequence of names separated by whitespace,
Each name will be looked up, and each of the associated functions will be applied successively,
from left to right.
a reference to a function
The provided function will be called on with each value in turn.
a reference to an array
Each item in the array will be expanded as provided above.
A fatal error will be generated if you pass an unsupported escape specification, or if the function
is called with multiple values in a scalar context.
String::Escape::names() : @defined_escapes
Returns a list of defined escape specification strings.
String::Escape::add( $escape_name, \&escape_function );
Add a new escape specification and corresponding function.
By default, all of the public functions described below are available as named escape commands, as well
as the following built-in functions:
• none: Return the string unchanged.
• uppercase: Calls the built-in uc function.
• lowercase: Calls the built-in lc function.
• initialcase: Calls the built-in lc and ucfirst functions.
Here are a few examples:
• "print escape('qprintable', "\tNow is the time\nfor all good folks\n" );"
"\tNow is the time\nfor all good folks\n"
• "print escape('uppercase qprintable', "\tNow is the time\nfor all good folks\n" );"
"\tNOW IS THE TIME\nFOR ALL GOOD FOLKS\n"
• "print join '--', escape('printable', "\tNow is the time\n", "for all good folks\n" );"
\tNow is the time\n--for all good folks\n
• You can add more escaping functions to the supported set by calling add().
"String::Escape::add( 'html', \&HTML::Entities::encode_entities );"
"print escape('html', "AT&T" );"
AT&T
Space-separated Lists and Hashes
@words = string2list( $space_separated_phrases );
Converts a space separated string of words and quoted phrases to an array;
$space_sparated_string = list2string( @words );
Joins an array of strings into a space separated string of words and quoted phrases;
%hash = string2hash( $string );
Converts a space separated string of equal-sign-associated key=value pairs into a simple hash.
$string = hash2string( %hash );
Converts a simple hash into a space separated string of equal-sign-associated key=value pairs.
%hash = list2hash( @words );
Converts an array of equal-sign-associated key=value strings into a simple hash.
@words = hash2list( %hash );
Converts a hash to an array of equal-sign-associated key=value strings.
Here are a few examples:
• "print list2string('hello', 'I move next march');"
hello "I move next march"
• "@list = string2list('one "second item" 3 "four\nlines\nof\ntext"');"
"print $list[1];"
second item
• "print hash2string( 'foo' => 'Animal Cities', 'bar' => 'Cheap' );"
foo="Animal Cities" bar=Cheap
• "%hash = string2hash('key=value "undefined key" words="the cat in the hat"');"
"print $hash{'words'};"
the cat in the hat
"print exists $hash{'undefined_key'} and ! defined $hash{'undefined_key'};"
1
SEE ALSO
Numerous modules provide collections of string escaping functions for specific contexts.
The string2list function is similar to to the quotewords function in the standard distribution; see
Text::ParseWords.
Use other packages to stringify more complex data structures; see Storable, Data::Dumper, or other
similar package.
BUGS
The following issues or changes are under consideration for future releases:
• Does this problem with the \r character only show up on Windows? (And is it, in fact, a feature
rather than a bug?)
http://rt.cpan.org/Public/Bug/Display.html?id=19766
• Consider changes to word parsing in string2list: Perhaps use \b word-boundary test in elide's regular
expression rather than \s|\Z? Perhaps quotes embedded in a word (eg: a@"!a) shouldn't cause phrase
breaks?
• Check for possible problems in the use of printable escaping functions and list2hash. For example,
are the encoded strings for hashes with high-bit characters in their keys properly unquoted and
unescaped?
• We should allow escape specifications to contain = signs and optional arguments, so that users can
request certain string lengths with "escape("lowercase elide=20 quoted", @_".
VERSION
This is version 2010.002.
INSTALLATION
This package should run on any standard Perl 5 installation.
To install this package, download the distribution from a CPAN mirror, unpack the archive file, and
execute the standard "perl Makefile.PL", "make test", "make install" sequence or your local equivalent.
SUPPORT
Once installed, this module's documentation is available as a manual page via "perldoc String::Escape" or
on CPAN sites such as "http://search.cpan.org/dist/String-Escape".
If you have questions or feedback about this module, please feel free to contact the author at the
address shown below. Although there is no formal support program, I do attempt to answer email promptly.
Bug reports that contain a failing test case are greatly appreciated, and suggested patches will be
promptly considered for inclusion in future releases.
You can report bugs and request features via the CPAN web tracking system at
"http://rt.cpan.org/NoAuth/ReportBug.html?Queue=String-Escape" or by sending mail to "bug-string-escape
at rt.cpan.org".
If you've found this module useful or have feedback about your experience with it, consider sharing your
opinion with other Perl users by posting your comment to CPAN's ratings system
("http://cpanratings.perl.org/rate/?distribution=String-Escape").
For more general discussion, you may wish to post a message on PerlMonks
("http://perlmonks.org/?node=Seekers%20of%20Perl%20Wisdom") or on the comp.lang.perl.misc newsgroup
("http://groups.google.com/group/comp.lang.perl.misc/topics").
AUTHOR
Matthew Simon Cavalletto, "<simonm at cavalletto.org>"
Initial versions developed at Evolution Online Systems with Eleanor J. Evans and Jeremy G. Bishop.
LICENSE
Copyright 2010, 2002 Matthew Simon Cavalletto.
Portions copyright 1996, 1997, 1998, 2001 Evolution Online Systems, Inc.
You may use, modify, and distribute this software under the same terms as Perl.
See http://dev.perl.org/licenses/ for more information.