Is there a command for checking alias existence in PowerShell?

You can use Test-Path for this:

PS C:\> test-path alias:l*
True
PS C:\> test-path alias:list*
False

Just use:

if (Test-Path alias:list*) { ... }

or

if(!(Test-Path alias:list*)) { ... }

if you want to do something when the alias doesn't exist.

As others wrote, Get-Alias works as well, but Test-Path will avoid building the list of aliases so might be every so slightly faster if you care about that.

Further explanation:

Powershell uses path names to access a lot more than just files, so while C: prefix lets you access files on drive C, alias: lets you access aliases, and other qualifers let you access things like functions, commands, registry keys, security certificates, and so on. So here, alias:l* is a wildcard pathname which will match all aliases that begin with the letter l in exactly the same way that C:l* would match all files beginning with l in the root of drive C.

Test-Path is a commandlet which tests whether the path refers to an existing object with a True result only if at least one existing object matches that path. So normally you would use it to test whether a file exists but equally you can test for existence of anything that is addressable with a suitable qualifier.

Yes, use the Get-Alias command.

Example:

Get-Alias -Name spps;

# If statement example
if (Get-Alias -Name spps) {
    # Do something here
}

To get a list of all commands that deal with aliases, use Get-Command

Get-Command -Name *alias;

I think Get-Alias is what you are looking for.

MS Documentation: http://technet.microsoft.com/en-gb/library/ee176839.aspx

Example for IF:

$ar = get-alias -name f* 
if($ar.count -lt 1){ do stuff }