interactive regular expression tool

[quadz]

Hola!

Pretty slick interactive tool for experimenting with regular expressions:

http://www.rubular.com/

Note: though it claims to be tailored toward ruby regular expressions, unless you get into the more esoteric features, ruby regexps are compatible with perl regexps (which are compatible with grep -E or sed).

So don't worry--if you don't currently know the difference between ruby/perl/grep/sed regexps, then what you learn here will most likely be applicable across the board.

Also -- pretty nice example of dynamic HTML on that site...!

Regards,

[reaper]

You could also use something like editpad pro so when you build the regex it highlights all the matches.

Here's matching an IP:
\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b

\b apply regex on word boundry

\.  matches on the literal period, the . will be there in decimal form ip to separate the four bytes

but matching on d{1,3}\. will only verify there is 1 to 3 digits then a period, so it will match 999.999.999.999 , and an ip cannot go passed 255 for the value of each byte since the whole ip address is base2 32 bits.

the patterns inside the paranthesis gets applied to match 0-255 ..[0-5] match a single digit 0 through 5 after 25 before the . in a word boundry.  The ? matches the preceding character zero or more times.  Then you can write them more efficient, and i'm not quiet sure how that works.

Then there is passing the parameters via the bash shell.

anything in the ' quotes is literal except \ when followed by a $ for variables or backticks for embedding a command or something like that, where data between " does expand variables and what not.

Well something like that

 

[[BTF]Sigma]

Brain =

[reaper]

The regular expression can be applied by something like a utility (egrep) that shows  lines in a file that match the pattern.  Certain characters in the expression have special meaning.

Like.
. = any one single character, but only one
the \ makes the character afterwards a literal character "\." is a real period
*,?, [ ] , (), {}, ^, and $ have special meaning to. like ^ is the start of what you apply the regex to, and $ the end.