Powershell pitfalls

Question

What Powershell pitfalls you have fall into? :-)

Mine are:

# -----------------------------------
function foo()
{
    @(\"text\")
}

# Expected 1, a         


        

Answer 1

There are some tricks to building command lines for utilities that were not built with Powershell in mind:

• To run an executable who's name starts with a number, preface it with an Ampersand (&).

& 7zip.exe

• To run an executable with a space anywhere in the path, preface it with an Ampersand (&) and wrap it in quotes, as you would any string. This means that strings in a variable can be executed as well.

# Executing a string with a space. & 'c:\path with spaces\command with spaces.exe'

# Executing a string with a space, after first saving it in a variable. $a = 'c:\path with spaces\command with spaces.exe' & $a

• Parameters and arguments are passed to legacy utilities positionally. So it is important to quote them the way the utility expects to see them. In general, one would quote when it contains spaces or does not start with a letter, number or dash (-).

C:\Path\utility.exe '/parameter1' 'Value #1' 1234567890

• Variables can be used to pass string values containing spaces or special characters.

$b = 'string with spaces and special characters (-/&)' utility.exe $b

• Alternatively array expansion can be used to pass values as well.

$c = @('Value #1', $Value2) utility.exe $c

• If you want Powershell to wait for an application to complete, you have to consume the output, either by piping the output to something or using Start-Process.

# Saving output as a string to a variable. $output = ping.exe example.com | Out-String

# Piping the output. ping stackoverflow.com | where { $_ -match '^reply' }

# Using Start-Process affords the most control. Start-Process -Wait SomeExecutable.com

• Because of the way they display their output, some command line utilities will appear to hang when ran inside of Powershell_ISE.exe, particularly when awaiting input from the user. These utilities will usually work fine when ran within Powershell.exe console.