Bash: Check if a string looks like a three part version number using a regular expression

Question

I need bash to check whether CI_COMMIT_REF_NAME matches either the string master, or a three part version number like 1.3.5, 1.1.11 and so on.

Here's what I tried:

#!/bin/bash
CI_COMMIT_REF_NAME=1.1.4
if [ $CI_COMMIT_REF_NAME == 'master' ] || [[ $CI_COMMIT_REF_NAME =~ ^([0-9]{1,2}\.){2}[0-9]{1,2}$ ]]
 then 
     echo "true"
 else 
     echo "false"
fi

The expected output is true, but I get false. Setting the variable to master works as intended, so the mistake must be my regex.

What am I doing wrong?

Wiktor Stribiżew · Accepted Answer · 2017-03-31 12:37:11Z

2

You need to declare the regex as a separate variable inside single quotes, there will be no issues parsing your regex in bash then and make sure the parentheses are placed around the [0-9]{1,2}\. part:

rx='^([0-9]{1,2}\.){2}[0-9]{1,2}$'
if [ $CI_COMMIT_REF_NAME == 'master' ] || [[ $CI_COMMIT_REF_NAME =~ $rx ]]

See the online Bash demo

Now, the pattern matches:

^ - start of string
([0-9]{1,2}\.){2} - 2 occurrences of 1 or 2 digits followed with a literal dot
[0-9]{1,2} - 1 or 2 digits
$ - end of string.

edited Mar 31, 2017 at 12:37

answered Mar 31, 2017 at 12:20

Wiktor Stribiżew

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2 Comments

Wiktor Stribiżew Over a year ago

I added the pattern description. And yes, the parentheses should enclose only the pattern you need to quantify.

Sebastian Schmied Over a year ago

Thanks for your help!

William Pursell · Accepted Answer · 2017-03-31 12:25:27Z

2

You probably don't want to match the beginning of the line twice:

$ CI_COMMIT_REF_NAME=1.1.4
$ [[ $CI_COMMIT_REF_NAME =~ (^[0-9]{1,2}\.){2}[0-9]{1,2}$ ]] && echo match
$ [[ $CI_COMMIT_REF_NAME =~ ^([0-9]{1,2}\.){2}[0-9]{1,2}$ ]] && echo match
match

answered Mar 31, 2017 at 12:25

William Pursell

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1 Comment

Sebastian Schmied Over a year ago

So there were actually two mistakes. Thank you!

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