Match Everything Until And Everything After With Regex Lookaheads And Lookbehind

The aim of this reference📚 is to provide a reference for PowerShell’s regex lookarounds, i.e.:

1. lookahead
2. lookbehind

1. regex: lookaheads and lookbehinds

• concepts to define patterns that only match they they
• are / are not followed by a certain pattern → lookahead (positive / negative)
• are / are not preceded by a certain pattern → lookbehind (positive / negative)

name       | pattern
-----------|-------------------------------------
lookahead  | MATCH_PATTERN(?=LOOKAHEAD_PATTERN)
lookbehind | (?<=LOOKBEHIND_MATTERN)MATCH_PATTERN

2. example: lookbehind with the lookup of a bucket from the HashiCorp Consul CV

• if I want to capture name that is after mr + an empty string (whitespace \s)
• i need to use lookbehind syntax

[regex]::matches(‘mr paul’,’(?<=mr\s).*’).value
→→→ paul

• I am getting the URL of the s3 bucket that is preceded by aws_setup_prod1/output/s3_bucket_kinesis_s3_enriched_id: with Hashicorp Consul in this way (and copy to clipboard for efficiency)

    $regex = "(?<=aws_setup_prod1/output/s3_bucket_kinesis_s3_enriched_id:).*"
    $returnedString = consul kv get -recurse customer/$consulName |
        Select-String -pattern $regex
        $streamingBucket = $returnedString.matches.value
        $streamingBucket | clip
        write-host $streamingBucket pasted to clipboard -foregroundcolor cyan