Item or array?

PowerShell cmdlets behave in interesting way. You can get an array or a single object from one method, so, be ready!
Innocent code snippet:

1. $processes = Get-Process -Name powershell* -Verbose  
2. If ($processes.count -gt 1) {  
3.     "There are several powershell consoles"  
4. } ElseIf ($processes.count -eq 1) {  
5.     "There is one powershell console"  
6. } Else {  
7.     "There are no powershell consoles at all"  
8. }  

What can go wrong?

But PowerShell runtime does a following thing:

• If cmdlet returns several objects, it wraps them in object[] 
• If only one object is returned to pipe, it returns the object itself (Process class instance in our case)
• If no results are returned, it returns $null

You will get  "There are no powershell consoles at all" when you have both 0 or 1 console.

The preferred way to work with cmdlet output is pipeline, so most clean and robust solution will be:

1. $powershellConsoles = 0  
2. Get-Process -Name powershell* | ForEach-Object { $powershellConsoles++ }  
3.   
4. # First way, generic    
5. If ($powershellConsoles -gt 1) {    
6.     "There are several powershell consoles"    
7. } ElseIf ($powershellConsoles -eq 1) {    
8.     "There is one powershell console"    
9. } Else {    
10.     "There are no powershell consoles at all"    
11. }  

Also, you can handle output like that:

1. $processes = Get-Process -Name powershell*
2.   
3. # First way, generic  
4. If ($processes -is [array]) {  
5.     "There are several powershell consoles"  
6. } ElseIf ($processes -ne $null) {  
7.     "There is one powershell console"  
8. } Else {  
9.     "There are no powershell consoles at all"  
10. }  
11.   
12. # Second way, straight typed  
13. If ($processes -is [array]) {  
14.     "There are several powershell consoles"  
15. } ElseIf ($processes -is [System.Diagnostics.Process]) {  
16.     "There is one powershell console"  
17. } Else {  
18.     "There are no powershell consoles at all"  
19. }  

Also, notice, that default cmdlets behavior is to write error, if explicit conditions were determined:

1. # Will silently return $null, if there are no jobs at all  
2. Get-Job  
3.   
4. # Will return null and error message, if there are no jobs reaching conditions  
5. Get-Job -Name NonexistableJob