diff options
| -rw-r--r-- | powershell.html.markdown | 44 |
1 files changed, 36 insertions, 8 deletions
diff --git a/powershell.html.markdown b/powershell.html.markdown index 7c54dc44..2d4c65b7 100644 --- a/powershell.html.markdown +++ b/powershell.html.markdown @@ -151,23 +151,47 @@ $null # => None # $null, 0, and empty strings and arrays all evaluate to False. # All other values are True +# $null, 0, and empty strings and arrays all evaluate to False. +# All other values are True function test ($value) { - if ($value) {Write-Output 'True'} - else {Write-Output 'False'} + if ($value) { + Write-Output 'True' + } + else { + Write-Output 'False' + } } + test ($null) # => False test (0) # => False test ("") # => False -test [] # => True +test [] # => True *[] Not valid in Powershell, creates null-valued expression test ({}) # => True test @() # => False +<# +IsPublic IsSerial Name BaseType +-------- -------- ---- -------- +True True Int32 System.ValueType +True True Int32 System.ValueType +True True String System.Object +You cannot call a method on a null-valued expression. +At line:4 char:1 ++ $test3.getType() ++ ~~~~~~~~~~~~~~~~ + + CategoryInfo : InvalidOperation: (:) [], RuntimeException + + FullyQualifiedErrorId : InvokeMethodOnNull + +True True ScriptBlock System.Object +True True Object[] System.Array +#> + #################################################### ## 2. Variables and Collections #################################################### # Powershell uses the "Write-Output" function to print -Write-Output "I'm Powershell. Nice to meet you!" # => I'm Powershell. Nice to meet you! +Write-Output "I'm Posh. Nice to meet you!" # => I'm Posh. Nice to meet you! # Simple way to get input data from console $userInput = Read-Host "Enter some data: " # Returns the data as a string @@ -367,7 +391,6 @@ switch($val) { { $_ -like 's*' } { "Case insensitive"; break } { $_ -clike 's*'} { "clike, ceq, cne for case sensitive"; break } { $_ -notmatch '^.*$'} { "Regex matching. cnotmatch, cnotlike, ..."; break } - { 'x' -contains 'x'} { "FALSE! -contains is for lists!"; break } default { "Others" } } @@ -384,7 +407,6 @@ finally { } - # Writing to a file $contents = @{"aa"= 12 "bb"= 21} @@ -532,6 +554,7 @@ True False Guitar Instrument #> + #################################################### ## 7. Advanced #################################################### @@ -582,7 +605,7 @@ $Area This is a silly one You may one day be asked to create a func that could take $start and $end and reverse anything in an array within the given range - based on an arbitrary array + based on an arbitrary array without mutating the original array Let's see one way to do that and introduce another data structure #> @@ -599,7 +622,7 @@ function Format-Range ($start, $end) { elseif ($index -ge $start -and $index -le $end) { $stack.Push($targetArray[$index]) } - elseif ($index -gt $end) { + else { $secondSectionArray.Add($targetArray[$index]) > $null } } @@ -607,6 +630,8 @@ function Format-Range ($start, $end) { Write-Output $returnArray } +Format-Range 2 6 # => 'a','b','g','f','e','d','c','h','i','j','k','l','m','n' + # The previous method works, but it uses extra memory by allocating new arrays # It's also kind of lengthy # Let's see how we can do this without allocating a new array @@ -623,10 +648,13 @@ function Format-Range ($start, $end) { } return $targetArray } + +Format-Range 2 6 # => 'a','b','g','f','e','d','c','h','i','j','k','l','m','n' ``` Powershell as a Tool: Getting Help: + ```Powershell # Find commands Get-Command about_* # alias: gcm |