CODEWITHSUNDEEP
regex
Deqing
Deqing

Reputation: 14632

regular expression - excluding specific chars

I am trying to write a regular expression matching a set without some chars.

For example, it matches [ a-zA-Z]* but excludes i,o,q,I,O,Q.

So: "A fat cat" matches, "Boy" doesn't.

Looks like it can be [ a-hj-npr-zA-HJ-NPR-Z]*.

Is there a simpler version for this?

Btw, I'm using it in PostgreSQL, but I think it should be a standard expression.

Upvotes: 0

Views: 261

Answers (3)

anubhava
anubhava

Reputation: 784888

You can use negative lookahead for this as Postgresql support lookaheads:

(?![ioqIOQ])[A-Za-z ]

To make it match complete line use:

^(?:(?![ioqIOQ])[A-Za-z ])+$

RegEx Demo

Upvotes: 1

phuzi
phuzi

Reputation: 13060

Don't need fancy lookaheads/behinds just use more, but smaller, character ranges.

You'll want something like ^[a-hj-npr-zA-HJ-NPR-Z ]*$.

Added a space to match sentences

You can see test this on-line here at debuggex

Upvotes: 1

tripleee
tripleee

Reputation: 189307

Based on @Anubhava's answer, but extending to an entire string rather than just one character,

^(?=[^ioqIOQ]*$)[ A-Za-z]*$

The (?=...) is a positive lookahead -- the opposite of the negative lookahead in Anubhava's answer. We are requiring all matches to also match the constraint [^ioqIOQ].

You could also implement the repetition over the entire string with

^((?![ioqIOQ])[ A-Za-z])*$

but it seems a lot less efficient. (I have not performed any timings, though.)

Upvotes: 1

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