Question ...??

[detroit]

Hi

Can anyone tell me what does this mean or what it does?

#define URL_REG_EXPR "[A-Za-z]+://[A-Za-z0-9_\\-\\+~.:?&@=/%#,;\\{\\}\\(\\)\\/*\\*/\\[\\]\\|\\*\\!\\\\]+"

Thanks

[kbw]

It's a regular expression for identifying a URL.

[A-Za-z]+ is any sequence of upper or lower case letters.
:// is a litteral.
These will match http:// or ftp:// and so on.

I'm sure you can determine the rest yourself with the extract below or looking at the manual page.

These are from the linux man page for grep:

REGULAR EXPRESSIONS
A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to
arithmetic expressions, by using various operators to combine smaller expressions.

grep understands three different versions of regular expression syntax: “basic,” “extended” and “perl.” In GNU grep,
there is no difference in available functionality between basic and extended syntaxes. In other implementations, basic
regular expressions are less powerful. The following description applies to extended regular expressions; differences
for basic regular expressions are summarized afterwards. Perl regular expressions give additional functionality, and
are documented in pcresyntax(3) and pcrepattern(3), but may not be available on every system.

The fundamental building blocks are the regular expressions that match a single character. Most characters, including
all letters and digits, are regular expressions that match themselves. Any meta-character with special meaning may be
quoted by preceding it with a backslash.

The period . matches any single character.

Character Classes and Bracket Expressions
A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list; if the
first character of the list is the caret ^ then it matches any character not in the list. For example, the regular
expression [0123456789] matches any single digit.

Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any
single character that sorts between the two characters, inclusive, using the locale's collating sequence and character
set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary
order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for
example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the
LC_ALL environment variable to the value C.

Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are
self explanatory, and they are [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:],
[:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the
current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (Note that the
brackets in these class names are part of the symbolic names, and must be included in addition to the brackets
delimiting the bracket expression.) Most meta-characters lose their special meaning inside bracket expressions. To
include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first.
Finally, to include a literal - place it last.

Anchoring
The caret ^ and the dollar sign $ are meta-characters that respectively match the empty string at the beginning and end
of a line.

The Backslash Character and Special Expressions
The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches
the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. The
symbol \w is a synonym for [_[:alnum:]] and \W is a synonym for [^_[:alnum:]].

Repetition
A regular expression may be followed by one of several repetition operators:
?
* The preceding item will be matched zero or more times.
+ The preceding item will be matched one or more times.
{n} The preceding item is matched exactly n times.
{n,} The preceding item is matched n or more times.
{n,m} The preceding item is matched at least n times, but not more than m times.

[detroit]

Thanks for the reply, very informative( more than I can handle).

I am stuck, trying to modify a matching braces code in notepad++ and used concept location and it took me to this line and thought it had anything to do with the function I am working on.
It looks like it does not have anything to do with me, i think.

Thanks again kbw