How to match "command line argument" style strings with regex?

Question

I'm trying to validate a string I use in one of my applications, and the structure of it is basically the same as linux command line arguments.

E.G -m -b -s etc...

I'm basically trying to make the pattern;

No space at the beginning but allow spaces inbetween words.
There must be a space before a - if it isn't the first -.
There should be no limit to how many you can enter as long as they fit the pattern. For example these would all be fine; -m -fd -optional but something like this wouldnt be; -m-fd teststring

I managed to get as far as ^-[a-zA-Z]\s but I'm not sure how to make this repeat! This also doesn't work on flags longer than 1 character and also has some issues with spaces!

To match such a line you could use ^-[^\s-][^-]*(?:\s-[^\s-][^-]*)*$ and to extract, you may use (?<!\S)-[^\s-][^-]* — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jul 29, 2020 at 13:57
@WiktorStribiżew Sorry I only got around to testing it now. Yes it does! Many Thanks! — Borassign
– Borassign, Commented Jul 30, 2020 at 5:50

Wiktor Stribiżew · Accepted Answer · 2020-07-30 07:46:46Z

1

To match and validate such a line you could use

^-[^\s-][^-]*(?:\s-[^\s-][^-]*)*$

See the regex demo.

To extract each option, you may use

(?<!\S)-[^\s-][^-]*

See this regex demo.

Details

^ - start of a string
- - a hyphen
[^\s-][^-]* - any char other than whitespace and - and then 0 or more chars othee than -
(?:\s-[^\s-][^-]*)* - 0 or more repetitions of
- \s - a whitespace
- - - a hyphen
- [^\s-][^-]* - any char other than whitespace and - and then 0 or more chars othee than -
$ - end of string.

answered Jul 30, 2020 at 7:46

Wiktor Stribiżew

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2 Comments

Borassign Over a year ago

Hey I found a bit of a flaw in this. With the example -m -fd teststring it matches when teststring should require a dash before it. Any ideas? :)

Wiktor Stribiżew Over a year ago

@Borassign Maybe you want ^-[^\s-]+(?:\s-[^\s-]+)*$ and (?<!\S)-[^\s-]+?

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