I would like to read an environment variable called "[TF]MYVAR" via PowerShell. However the following syntax does not work:
$env:[TF]MYVAR
It yields the following error:
Missing or invalid array index expression.
Also adding quitation marks (-> "$env:[TF]MYVAR") does not help.
The square brackets are confusing the command line parser. Try the alternate variable syntax:
${<variable name>}
See also Get-Help about_Variables.
As @PetSerAl notes below, due to how the command line parser deals with escaping square bracket characters, you'll need to do this:
${env:``[TF``]MYVAR}
You can also use the native .Net methods, which work without needing to be escaped:
[System.Environment]::GetEnvironmentVariable('[TF]MYVAR')
env:[TF]MYVAR, but we're looking for the value of the item [TF]MYVAR in the Env: drive. The least verbose thing I found that does that is gc env:'`[TF`]MYVAR', but there ought to be something better.
${ } syntax has multiple uses in PowerShell. Please read the Get-Help entry for about_Variables under the heading for variables with special characters.
env:[TF]MYVAR it need to be ${variable:env:[TF]MYVAR}.cmd shell and issuing set [TF]MYVAR=3, then executing powershell and typing ${env:[TF]MYVAR} gives nothing. This is PowerShell 5.1, incidentally. @PetSerAl: well the plot thickens, because yes, that does read the variable, while apparently ${env:[TF]MYVAR} reads... nothing at all.${env:``[TF``]MYVAR} to work properly in that case.