What does the underscore mean in the following regex?
[a-zA-Z0-9_]
The _ seems to make no difference so I don't understand the purpose of it.
views:
608answers:
5Although, I wish it had been phrased "underscore is underscore" :-)
pst
2009-10-21 23:00:36
Try as a might, I couldn't find a single problem with your statement; it's utter simplicity and logic is beyond reproach :-) +1
paxdiablo
2009-10-21 23:13:21
And never before was the rep cap so easily hit...
Ether
2009-10-22 02:19:18
I just gave you a populist badge, by up-voting the accepted answer.
Brad Gilbert
2009-10-22 04:29:58
+24
A:
It means to match the underscore character in addition to lowercase letters, uppercase letters, and numbers.
No Surprises
2009-10-21 22:58:41
+7
A:
With the exception of character sequences ([., [:, and [=), range expressions (e.g., [a-z]), and the circumflex in the beginning ([^), every character inside a bracket expression means the character itself, just like that underscore.
As a side note, that expression is commonly represented by \w (word character, ignoring unicode and locale), and is commonly used to define the set of characters that are allowed to be used in variable names.
JG
2009-10-21 23:08:25
For most languages, `[a-zA-Z_][a-zA-Z0-9_]*` is probably more accurate for variable names since they prohibit starting with digits.
Tim Hatch
2009-10-21 23:51:47
And many languages nowadays allow other scripts for variable names as well. So Have fun with Unicode classes as well :-)
Joey
2009-10-22 05:50:34
+9
A:
Regular expressions are documented in perlre. That's the place to check whenever you have a question about regular expressions. The Regular-Expressions.info site is very helpful too.
To get you started, the thing you are looking at is called a "character class".
brian d foy
2009-10-22 02:04:16
For someone new to regular expressions in Perl, I always recommend `perldoc perlrequick` first. It's a lot more friendly than `perldoc perlre` - mostly because it's not so overwhelmingly detailed.
Telemachus
2009-10-22 19:40:54