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How to extract with regexp in ansible numbers from hostname without one specific – Nginx

How I can extract with regexp from hostname number without one from domain. Examples:

nginx-node-01.prd1.com
nginx-node-10.prd1.com

And I need extract only number after nginx-node-, without number from "prd".

When I do this regexp

{{ inventory_hostname | regex_replace('[^0-9]') }}

I get output like this

011
101

Thanks for any help!

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2

Answers


  1. 0

    Instead of removing all non digits, you can match the format of the string and capture the digits in a group, and use that group in the replacement.

    ^w+(?:-w+)+-(d+).S+$

    The pattern matches:

    • ^ Start of string
    • w+ Match 1+ word characters
    • (?:-w+)+ Repeat 1+ times a - and 1+ word characters
    • -(d+) Match - and capture 1+ digits in group 1
    • .S+ match 1 . and 1+ non whitespace chars
    • $ End of string

    Regex demo

    Output

    01
10

    For example

    {{ inventory_hostname | regex_replace('^\w+(?:-\w+)+-(\d+)\.\S+$', '\1') }}

    Another option might be regex_search and match 1+ digits between - and . using lookarounds.

    (?<=-)\d+(?=\.)

    Regex demo

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  2. 0

    Since these strings look very well-structured, you may leverage that and simply remove all chars from the beginning till the first digit with ^D+ pattern and all chars till the end of string from the first dot using ..* pattern, combined with the | alternation operator:

    {{ inventory_hostname | regex_replace('^\D+|\..*', '') }}

    See the regex demo.

    Details:

    • ^ – start of string
    • D+ – one or more chars other than a digit
    • | – or
    • . – a dot
    • .* – any zero or more chars other than line break chars as many as possible.
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