diff options
Diffstat (limited to 'powershell.html.markdown')
| -rw-r--r-- | powershell.html.markdown | 79 |
1 files changed, 44 insertions, 35 deletions
diff --git a/powershell.html.markdown b/powershell.html.markdown index 033d6c25..5116fac8 100644 --- a/powershell.html.markdown +++ b/powershell.html.markdown @@ -21,7 +21,6 @@ rather than plain text. After years of evolving, it resembles Python a bit. Powershell as a Language: ```powershell - # Single line comments start with a number symbol. <# @@ -118,14 +117,15 @@ $False - 5 # => -5 2 -lt 3 -and 3 -lt 2 # => False # (-is vs. -eq) -is checks if two objects are the same type. -# -eq checks if the objects have the same values. +# -eq checks if the objects have the same values, but sometimes doesn't work +# as expected. # Note: we called '[Math]' from .NET previously without the preceeding # namespaces. We can do the same with [Collections.ArrayList] if preferred. [System.Collections.ArrayList]$a = @() # Point a at a new list $a = (1,2,3,4) $b = $a # => Point b at what a is pointing to $b -is $a.GetType() # => True, a and b equal same type -$b -eq $a # => True, a and b values are equal +$b -eq $a # => None! See below [System.Collections.Hashtable]$b = @{} # => Point a at a new hash table $b = @{'one' = 1 'two' = 2} @@ -154,6 +154,13 @@ $age = 22 "$name's name is $($name.Length) characters long." # => "Steve's name is 5 characters long." +# Strings can be compared with -eq, but are case insensitive. We can +# force with -ceq or -ieq. +"ab" -eq "ab" # => True +"ab" -eq "AB" # => True! +"ab" -ceq "AB" # => False +"ab" -ieq "AB" # => True + # Escape Characters in Powershell # Many languages use the '\', but Windows uses this character for # file paths. Powershell thus uses '`' to escape characters @@ -221,7 +228,7 @@ $defaultArray.Add("thing4") # => Exception "Collection was of a fixed size." # ArrayLists store sequences [System.Collections.ArrayList]$array = @() # You can start with a prefilled ArrayList -[System.Collections.ArrayList]$otherArray = @(4, 5, 6) +[System.Collections.ArrayList]$otherArray = @(5, 6, 7, 8) # Add to the end of a list with 'Add' (Note: produces output, append to $null) $array.Add(1) > $null # $array is now [1] @@ -237,25 +244,14 @@ $array.Add(3) > $null # array is now [1, 2, 4, 3] again. $array[0] # => 1 # Look at the last element $array[-1] # => 3 - # Looking out of bounds returns nothing $array[4] # blank line returned -# You can look at ranges with slice syntax. -# The start index is included, the end index is not -# (It's a closed/open range for you mathy types.) -$array[1..3] # Return array from index 1 to 3 => [2, 4] -$array[2..-1] # Return array starting from index 2 => [4, 3] -$array[0..3] # Return array from beginning until index 3 => [1, 2, 4] -$array[0..2] # Return array selecting every second entry => [1, 4] -$array.Reverse() # mutates array to reverse order => [3, 4, 2, 1] -# Use any combination of these to make advanced slices - -# Remove arbitrary elements from a array with "del" -$array.Remove($array[2]) # $array is now [1, 2, 3] +# Remove elements from a array +$array.Remove($array[3]) # $array is now [1, 2, 4] -# Insert an element at a specific index -$array.Insert(1, 2) # $array is now [1, 2, 3] again +# Insert at index an element +$array.Insert(2, 3) # $array is now [1, 2, 3, 4] # Get the index of the first item found matching the argument $array.IndexOf(2) # => 1 @@ -263,17 +259,29 @@ $array.IndexOf(6) # Returns -1 as "outside array" # You can add arrays # Note: values for $array and for $otherArray are not modified. -$array + $otherArray # => [1, 2, 3, 4, 5, 6] +$array + $otherArray # => [1, 2, 3, 4, 5, 6, 7, 8] # Concatenate arrays with "AddRange()" -$array.AddRange($otherArray) # Now $array is [1, 2, 3, 4, 5, 6] +$array.AddRange($otherArray) # Now $array is [1, 2, 3, 4, 5, 6, 7, 8] # Check for existence in a array with "in" 1 -in $array # => True # Examine length with "Count" (Note: "Length" on arrayList = each items length) -$array.Count # => 6 +$array.Count # => 8 +# You can look at ranges with slice syntax. +$array[1,3,5] # Return selected index => [2, 4, 6] +$array[1..3] # Return from index 1 to 3 => [2, 3, 4] +$array[-3..-1] # Return from last 3 to last 1 => [6, 7, 8] +$array[-1..-3] # Return from last 1 to last 3 => [8, 7, 6] +$array[2..-1] # Return from index 2 to last (NOT as most expect) => [3, 2, 1, 8] +$array[0,2+4..6] # Return multiple ranges with the + => [1, 3, 5, 6, 7] + +# -eq doesn't compare array but extract the matching elements +$array = 1,2,3,1,1 +$array -eq 1 # => 1,1,1 +($array -eq 1).Count # => 3 # Tuples are like arrays but are immutable. # To use Tuples in powershell, you must use the .NET tuple class. @@ -284,13 +292,14 @@ $tuple.Item(0) = 3 # Raises a TypeError # You can do some of the array methods on tuples, but they are limited. $tuple.Length # => 3 $tuple + (4, 5, 6) # => Exception -$tuple[0..2] # => $null +$tuple[0..2] # => $null (in powershell 5) => [1, 2, 3] (in powershell 7) 2 -in $tuple # => False -# Hashtables store mappings from keys to values, similar to Dictionaries. +# Hashtables store mappings from keys to values, similar to (but distinct from) Dictionaries. +# Hashtables do not hold entry order as arrays do. $emptyHash = @{} -# Here is a prefilled dictionary +# Here is a prefilled hashtable $filledHash = @{"one"= 1 "two"= 2 "three"= 3} @@ -299,7 +308,6 @@ $filledHash = @{"one"= 1 $filledHash["one"] # => 1 # Get all keys as an iterable with ".Keys". -# items maintain the order at which they are inserted into the dictionary. $filledHash.Keys # => ["one", "two", "three"] # Get all values as an iterable with ".Values". @@ -307,18 +315,18 @@ $filledHash.Values # => [1, 2, 3] # Check for existence of keys or values in a hash with "-in" "one" -in $filledHash.Keys # => True -1 -in $filledHash.Values # => False +1 -in $filledHash.Values # => False (in powershell 5) => True (in powershell 7) # Looking up a non-existing key returns $null $filledHash["four"] # $null -# Adding to a dictionary +# Adding to a hashtable $filledHash.Add("five",5) # $filledHash["five"] is set to 5 $filledHash.Add("five",6) # exception "Item with key "five" has already been added" -$filledHash["four"] = 4 # $filledHash["four"] is set to 4, running again does nothing +$filledHash["four"] = 4 # $filledHash["four"] is set to 4, running again does nothing -# Remove keys from a dictionary with del -$filledHash.Remove("one") # Removes the key "one" from filled dict +# Remove keys from a hashtable +$filledHash.Remove("one") # Removes the key "one" from filled hashtable #################################################### @@ -574,7 +582,7 @@ Get-Process | Foreach-Object ProcessName | Group-Object 1..10 | ForEach-Object { "Loop number $PSITEM" } 1..10 | Where-Object { $PSITEM -gt 5 } | ConvertTo-Json -# A notable pitfall of the pipeline is it's performance when +# A notable pitfall of the pipeline is its performance when # compared with other options. # Additionally, raw bytes are not passed through the pipeline, # so passing an image causes some issues. @@ -661,11 +669,12 @@ function Format-Range ($start, $end) { Format-Range 2 6 # => 'a','b','g','f','e','d','c','h','i','j','k','l','m' ``` + Powershell as a Tool: Getting Help: -```Powershell +```powershell # Find commands Get-Command about_* # alias: gcm Get-Command -Verb Add @@ -682,7 +691,7 @@ Update-Help # Run as admin If you are uncertain about your environment: -```Powershell +```powershell Get-ExecutionPolicy -List Set-ExecutionPolicy AllSigned # Execution policies include: @@ -696,7 +705,7 @@ help about_Execution_Policies # for more info $PSVersionTable ``` -```Powershell +```powershell # Calling external commands, executables, # and functions with the call operator. # Exe paths with arguments passed or containing spaces can create issues. |