How do I create a temporary path within a PowerShell script?

September 19, 2023

Given the code below, how do I set a variable that I can use to call the 7z executable? The env:Path approach at the top works once but then the terminal must be reloaded or the command cannot be found. Powershell seems to be treating it as a string, not as an executable call. Ultimately, I need to be able to pull this value in from the environment.

# $env:Path += "C:\Program Files\7-Zip"
# works once, then the terminal must be reloaded

$7zip = "C:\Program Files\7-Zip\7z.exe"
$dirAsStr = "C:\Program Files\7-Zip\7z.exe"
$dirAsDir = Get-Item $dirAsStr

$extract_files = "somewhere"
$output = "someplace"

# $dirAsDir a -t7z $output\format_files.7z $extract_files\format.*
# ParserError: Unexpected token 'a' in expression or statement.
# $7zip a -t7z $output\format_files.7z $extract_files\format.*
# ParserError: Unexpected token 'a' in expression or statement.

C:\"Program Files"\7-Zip\7z.exe a -t7z $output\format_files.7z $extract_files\format.*
# works fine

>Solution :

$env:Path += "C:\Program Files\7-Zip"

should be $env:Path += ";C:\Program Files\7-Zip" (note the ;) and it is effective for the remainder of the current session (process) only.

That is, you can then invoke 7-Zip as 7z ... in the same session.

If you want this modification to persist, i.e. to be available in all future sessions:

Either: Place the command in your $PROFILE file.
Or: Modify the persistent definition of the Path environment variable in the registry, e.g. interactively via sysdm.cpl
- Note: Robustly updating Path programmatically is nontrivial, unfortunately – see this answer.

$7zip a -t7z...

In order to execute commands whose names or paths are stored in variables, you must invoke them via &, the call operator (which is a syntactic necessity in PowerShell):

& $7zip a -t7z ...

The same goes for command names or paths that are quoted as a whole:

C:\"Program Files"\7-Zip\7z.exe happens to work without &, because the argument starts with an unquoted string.
By contrast, "C:\Program Files"\7-Zip\7z.exe" would require &