Escape space and resolve variable in Jenkins powershell script not working

The 7z.exe path in your first command has an extraneous trailing \, which causes problems:

cmd /c "C:\\Program Files\\7-Zip\\7z.exe\\"  # <- trailing \\ shouldn't be there

In your 2nd command, you're using single quotes around the command passed to cmd /c ('...'), but the contents of '...' strings in PowerShell are treated as literals, which explains why $fileName was not expanded (interpolated);
only double-quoted ("...") strings and, within limits, unquoted command arguments are expanded in PowerShell; e.g., compare the output from Write-Output '$HOME' to the output from Write-Output "$HOME" / Write-Output $HOME.

As iRon mentions, there's no need to involve cmd at all - PowerShell is perfectly capable of executing command-line programs directly, so this should work:

Invoke-Command -Session $session -ScriptBlock { & "C:\\Program Files\\7-Zip\\7z.exe" x C:\\Data\\Install\\$using:filename -oC:\\data\\install\\test -aoa >$null }

• Due to invoking 7z.exe directly, now there's no outer quoting needed anymore, and $fileName should be expanded.

  • Note, however, that $fileName was replaced with $using:fileName, which is necessary in order for the target session to know about the local $fileName variable - see Get-Help about_Remote_Variables.

• Since the 7z.exe file path is quoted (of necessity, due to containing spaces), you must use &, the call operator, to invoke it.

• Since the > redirection is now performed by PowerShell itself, the cmd-style >NUL output suppression was replaced with its PowerShell analog, >$null.

I wonder if it necessarily at all to invoke a CMD shell for this.I guess it would be simpler to directly invoke the 7z.exe with its parameters.

Nevertheless, you can build you own script block like this:

[ScriptBlock]::Create('cmd /c "C:\\Program Files\\7-Zip\\7z.exe" x C:\\Data\\Install\\' + $filename + ' -oC:\\data\\install\\test -aoa >NUL')