Get part of a string from the output of Get-Item in Powershell

Question

My powershell command below

$BUILD_SOURCEVERSIONMESSAGE= (Get-Item Env:\BUILD_SOURCEVERSIONMESSAGE)

returns output in this format

2018-10-26T01:08:44.7409834Z BUILD_SOURCEVERSIONMESSAGE     Merge 569594f057e2c4bd0320159855e81e14216ca66f into 41107d0f0db5ef2986831db2182280e0c...

I am trying to parse the string 569594f057e2c4bd0320159855e81e14216ca66f from the output above.

I tried converting the output to a string, splitting it on whitespace, and accessing the second element of the array as follows. However, I get empty string. How can I access the required string?

echo $BUILD_SOURCEVERSIONMESSAGE
$out = $BUILD_SOURCEVERSIONMESSAGE | Out-String
$out1 = $out.split()
echo $out1[1]

mklement0 · Accepted Answer · 2018-10-26 02:39:43Z

The concise equivalent of command Get-Item Env:\BUILD_SOURCEVERSIONMESSAGE - i.e., retrieving the value of environment variable BUILD_SOURCEVERSIONMESSAGE - is the expression $env:BUILD_SOURCEVERSIONMESSAGE.

Using the unary form of Powershell's -split operator, which splits the input by any nonempty run of whitespace (while stripping leading and trailing whitespace), you can get the desired output as follows:

PS> (-split $env:BUILD_SOURCEVERSIONMESSAGE)[3]
569594f057e2c4bd0320159855e81e14216ca66f

Index 3 extracts the 4th token resulting from the tokenization via -split.

If you want to use string interpolation with the result:

$prefix = 'before<'; $postfix = '>after'
$val = (-split $env:BUILD_SOURCEVERSIONMESSAGE)[3]

# Output a synthesized string that applies a pre- and postfix, using
# {...} to enclose variable names to avoid ambiguity.
"${prefix}${val}${postfix}"

The above yields:

before<569594f057e2c4bd0320159855e81e14216ca66f>after

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