Generate random string based on Regex?

Question

I wonder if there is a way to generate random string from a regex like:

/[a-z0-9]{5}/.to_s
#=> "dsar3"

I found randexp (https://github.com/benburkert/randexp) but it seems to not work with a basic example like above and anyway I feel it's left abandoned.

Anyone?

@iAmRubuuu This is not really random and is determined by a pattern instead. — squiguy
– squiguy, Commented Apr 7, 2013 at 7:20
It would need some basic constraints, right? I mean, there's no way to generate a random regex that matchs /.*/, since the number of characters involved could be any length between 0 an infinite. Should the number of characters be random also, or should we be trying to randomly select a value from an infinite set? Or are you suggesting a constraint wherein the regex could not allow things like * or + (as is the case with your example)? — Jun-Dai Bates-Kobashigawa
– Jun-Dai Bates-Kobashigawa, Commented Apr 14, 2013 at 23:58
Also, if you had .to_s on a regex provide a random matching string, that'd be a pretty serious wtf for the next developer that saw that code. — Jun-Dai Bates-Kobashigawa
– Jun-Dai Bates-Kobashigawa, Commented Apr 15, 2013 at 0:00

szabgab · Accepted Answer · 2014-04-05 21:04:48Z

4

Perl has a CPAN module that can do this. It works by converting the regex into a generative grammar. The concept can probably be adapted to Ruby, but would be a little work.

See http://metacpan.org/pod/Parse::RandGen and http://metacpan.org/pod/Parse::RandGen::Regexp

edited Apr 5, 2014 at 21:04

szabgab

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answered Apr 7, 2013 at 7:13

Neil Slater

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Comments

pguardiario · Accepted Answer · 2013-04-07 07:39:47Z

2

No but how about:

(0..255).map(&:chr).select{|x| x =~ /[a-z0-9]/}.sample(5).join
#=> "qif0l"

answered Apr 7, 2013 at 7:39

pguardiario

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4 Comments

Arup Rakshit Over a year ago

what the x =~ /[a-z0-9]/ is doing logically?

pguardiario Over a year ago

It's selecting only chars that match the regex

steenslag Over a year ago

sample does not allow duplicates, so "qqf01" would never happen.

pguardiario Over a year ago

Well there's a simple workaround if you really need duplicates.

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