This is a Random String Generator based on Regular Expression.
The idea is simple: Given a regular expression, generate random strings that can match it.
For example, to generate 5 random IP addresses that have all same components, we can use this:
$ echo "^(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(?:\.\1){3}$" | ./regxstr 5
250.250.250.250
213.213.213.213
4.4.4.4
118.118.118.118
2.2.2.2
No surprising, the above regular expression matches an IP address with 4 same dot parts. Isn't it cool?
regxstring can do much more. You can try more complex regular expressions. Basically, most Perl 5 supported regular expressions are also supported by regxstring, as showing bellow:
Meta-character(s) Description
--------------------------------
\ Quote the next meta-character
^ Match the beginning of the line
$ Match the end of the line (or before newline at the end)
? Match 1 or 0 times
+ Match 1 or more times
* Match 0 or more times
{n} Match exactly n times
{n,} Match at least n times
{n,m} Match at least n but not more than m times
. Match any character (except newline)
(pattern) Grouping
(?:pattern) This is for clustering, not capturing; it groups sub-expressions like "()", but doesn't make back-references as "()" does
(?=pattern) A zero-width positive look-ahead assertion, e.g., \w+(?=\t) matches a word followed by a tab, without including the tab
(?!pattern) A zero-width negative look-ahead assertion, e.g., foo(?!bar) matches any occurrence of "foo" that isn't followed by "bar"
| Alternation
[xyz] Matches a single character that is contained within the brackets
[^xyz] Matches a single character that is not contained within the brackets
[a-z] Matches a single character that is in a given range
[^a-z] Matches a single character that is not in a given range
\f Form feed
\n Newline
\r Return
\t Tab
\v Vertical white space
\d Digits, [0-9]
\D Non-digits, [^0-9]
\s Space and tab, [ \t\r\n\f]
\S Non-white space characters, [^ \t\r\n\f]
\w Alphanumeric characters plus '_', [0-9a-zA-Z_]
\W Non-word characters, [^0-9a-zA-Z_]
\N Matches what the Nth marked sub-expression matched, where N is a digit from 1 to 9
One more notice, regxstring also includes a library that allows you to generate such strings in your C/C++ programs.
Please enjoy yourself!