GNU/Linux man pages

Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :

ISBN : 978-2-7460-9712-4
EAN : 9782746097124
(Editions ENI)


CentOS 2.1AS







URI: :Escape − Escape and unescape unsafe characters


 use URI::Escape;
 $safe = uri_escape("10% is enough\n");
 $verysafe = uri_escape("foo", "\0-\377");
 $str  = uri_unescape($safe);


This module provides functions to escape and unescape URI strings as defined by RFC 2396. URIs consist of a restricted set of characters, denoted as "uric" in RFC 2396. The restricted set of characters consists of digits, letters, and a few graphic symbols chosen from those common to most of the character encodings and input facilities available to Internet users:

  "A" .. "Z", "a" .. "z", "0" .. "9",
  ";", "/", "?", ":", "@", "&", "=", "+", "$", ",",   # reserved
  "-", "_", ".", "!", "~", "*", "’", "(", ")"

In addition any byte (octet) can be represented in a URI by an escape sequence; a triplet consisting of the character "%" followed by two hexadecimal digits. Bytes can also be represented directly by a character using the US-ASCII character for that octet (iff the character is part of "uric").

Some of the "uric" characters are reserved for use as delimiters or as part of certain URI components. These must be escaped if they are to be treated as ordinary data. Read RFC 2396 for further details.

The functions provided (and exported by default) from this module are:
uri_escape($string, [$unsafe])

This function replaces all unsafe characters in the $string with their escape sequences and returns the result.

The uri_escape() function takes an optional second argument that overrides the set of characters that are to be escaped. The set is specified as a string that can be used in a regular expression character class (between [ ]). E.g.:

  "\x00-\x1f\x7f-\xff"          # all control and hi-bit characters
  "a-z"                         # all lower case characters
  "^A-Za-z"                     # everything not a letter

The default set of characters to be escaped is all those which are not part of the "uric" character class shown above.


Returns a string with all %XX sequences replaced with the actual byte (octet).

This does the same as:

   $string =~ s/%([0-9A-Fa-f]{2})/chr(hex($1))/eg;

but does not modify the string in-place as this RE would. Using the uri_unescape() function instead of the RE might make the code look cleaner and is a few characters less to type.

In a simple benchmark test I made I got something like 40% slowdown by calling the function (instead of the inline RE above) if a few chars where unescaped and something like 700% slowdown if none where. If you are going to unescape a lot of times it might be a good idea to inline the RE .

If the uri_unescape() function is passed multiple strings, then each one is unescaped returned.

The module can also export the "%escapes" hash which contains the mapping from all 256 bytes to the corresponding escape code. Lookup in this hash is faster than evaluating "sprintf("%%%02X", ord($byte))" each time.


the URI manpage


Copyright 1995−2000 Gisle Aas.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.