CODEWITHSUNDEEP
powershell
Gene Parmesan
Gene Parmesan

Reputation: 337

Powershell match operator on cmdlet output OR variable name for pipeline output?

I have a simple executable that runs, returns a few lines of code.

I need to grab a section of hex out of that line and store it in a variable.

I have something that works, but would like to make it cleaner? or one line?

The output is several lines, I only care about the one with the hex code. Typical return string

Info: Download of filename (0xff77) completed

$test1 = .\some.exe 2>&1 | Select-String -Pattern "0x"
$test1 -match "[0-9a-fA-F]{4}"
$test1 = $Matches[0]

I tried piping the output of the first line like so

$test1 = .\some.exe 2>&1 | Select-String -Pattern "0x" | -match "[0-9a-fA-F]{4}"

Obviously that didnt work, and I cant find much else on a better way to do this.

Is there a way to address the result of the previous pipeline to pass it to the match command?

$test1 = .\some.exe 2>&1 | Select-String -Pattern "0x" | $HiddenPrevPipeVar -match "[0-9a-fA-F]{4}"

What I want my $test1 to be equal to is the hex code ff77

Upvotes: 2

Views: 642

Answers (1)

mklement0
mklement0

Reputation: 439587

Let Select-String perform the regex matching for you:

$test1 =
  (.\some.exe 2>&1 | Select-String -Pattern '(?<=0x)[0-9a-f]+').Matches.Value

  • Select-String outputs Microsoft.PowerShell.Commands.MatchInfo instances describing each match, and its .Matches property contains a collection of System.Text.RegularExpressions.Match instances describing what the regex passed to -Pattern matched. The .Value property of each such instance contains the matched text.

  • While it is possible to use capture groups ((...)) in the regex and reference what they captured via .Matches as well, in this case it is simpler to use a positive look-behind assertion ((?<=...)) in order to effectively exclude 0x from the match reported in .Value

  • Also note that Select-String, like PowerShell in general, is case-insensitive by default, so that [a-f] in the regex covers both lowercase and uppercase letters.

Upvotes: 4

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