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jeikabu
jeikabu

Posted on • Originally published at rendered-obsolete.github.io on

PowerShell Crash Course (Part 2)

#devops #powershell #scripting

I’ve remained committed to improving my powershell game. Reaching for it instead of shoddy bat files whenever possible. There’s a bunch of things that didn’t make it into the first post, including a few things that inadvertantly got left out (e.g. copying files, other loops, etc.). So, I updated that post so it covers basic syntax and core command-line functionality. This post covers mostly auxillary features and utility commands.

time/wc 

# time; measure duration of command
Measure-Command { make }
# ls -1; count files in directory
Get-ChildItem | Measure-Object
# wc; count number of lines in file
Get-Content ./Cargo.toml | Measure-Object -Line
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https://devblogs.microsoft.com/scripting/maximizing-the-power-of-here-string-in-powershell-for-configuration-data/

&&

PowerShell is nice and all, but one of the things I missed most from bash et al. is the ability to chain commands on success/failure like make clean && make.

Thanks to PowerShell Core being open-source, pwsh joins the party as of 7.0.0-preview.5 so you can do things like:

# Create directory and enter it
New-Item -Type Directory blah && Set-Location blah
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If you’re using Windows Terminal, preview 1910 (or newer) should auto-detect it. For older releases, V > Settings (or Ctrl+,) to open profiles.json:

{
    "...": "...",
    "profiles" : 
    [
        {
            "...": "...",
            "commandline" : "C:\\Program Files\\PowerShell\\7-preview\\pwsh.exe",
            "name" : "PowerShell Core",
            "...": "...",
        },
    ]
}
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For Visual Studio Code, View > Command Palette (Ctrl+Shift+P) and type select default shell. It should present a drop-down list of options including the version you just installed. You may need to restart VS Code to change the current shell.

Opening a new terminal should now display:

PowerShell 7.0.0-preview.5
Copyright (c) Microsoft Corporation. All rights reserved.
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Filtering, substrings, grep, awk

When looking for substrings, make sure you use -like not -contains (which is for collections). Contrast:

$string = "windows-2019"
$string -contains '*2019*' # False
$string -like '*2019*' # True
$string -like '2019' # False
$string.Contains('*2019*') # False
$string.Contains('2019') # True

# Get first item of output
Get-ChildItem | select -First 1
Get-ChildItem | Select-Object -First 1
# Get certain properties of output
(Get-ChildItem).FullName
Get-ChildItem | % { $_.FullName }
Get-ChildItem | Select-Object -ExpandProperty FullName

# grep; find text in files
Select-String -Path ./src/*.rs -Pattern 'let'
# Find text in output
(Get-ChildItem).FullName | Select-String Cargo.*

# Split a string
$x = "0 1 2 3"
-split $x
# Split using explicit delimiter
"0,1,2,3" -split ','
# Split and return specific items
(-split $x)[0,-1] # 0 3
(-split $x)[-2..-1] # 2 3
(-split $x)[0,1+2..3] # all
(-split $x)[2..3+0] # 2 3 0
# WARNING: The following DON'T work
(-split $x)[0+2..3]
(-split $x)[0,2..3]
(-split $x)[2..3,0]
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Formatting 

# Output certain columns
Get-ChildItem | Format-Table Name, Size
"{1} {0}" -f "A", "B" # B A
"{0:X8}" -f 42 # 0000002A
[String]::Format("{0:x8}", 42) # 0000002a

# Convert to json
Get-ChildItem | Format-Table Name, Size | ConvertTo-Json
# Parse json file and get "tasks" field
(Get-Content ./.vscode/tasks.json | ConvertFrom-Json).tasks
# Parse key-value pairs as hashtable
'{ "key":"value1", "Key":"value2" }' | ConvertFrom-Json -AsHashtable
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Aliases/which/whereis

Get-Alias:

# List all aliases
alias
Get-Alias
# Get alias for `Get-Command`
Get-Alias -Definition Get-Command
# Get aliases matching `gc*`
Get-Alias gc*
Get-Alias -Name gc*
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which and whereis from this SO:

# All "gcc*" commands
Get-Command gcc*
# As a nicer table
Get-Command gcc* | Format-Table Name, Path
# Full path to first `cargo`
Get-Command cargo | Select-Object -First 1 -ExpandProperty Path
# Execute it
& $(Get-Command cargo | Select-Object -First 1 -ExpandProperty Path)
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Profiles

Profiles are scripts that run when PowerShell starts (like .bashrc etc.). $profile is the current profile:
Win10 $home\Documents\PowerShell\Microsoft.PowerShell_profile.ps1
Linux/MacOS $home/.config/powershell/Microsoft.PowerShell_profile.ps1

This is where you can set Set-PSReadLineOption and other environment/session customizations.

More Loops 

Get-Alias -Definition "*ForEach*"

CommandType Name Version Source
----------- ---- ------- ------
Alias % -> ForEach-Object
Alias foreach -> ForEach-Object
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Repeat something X times:

0..10 | % {
    # Commands to repeat here
}
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Archives

Expand-Archive:

# Extract to bundle/
Expand-Archive bundle.zip
# Extract to path
Expand-Archive bundle.zip .
Expand-Archive bundle.zip -DestinationPath .
# Extract multiple files
Get-ChildItem $Home/Downloads -Filter *.zip | Expand-Archive -DestinationPath output/ -Force
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If you’ve got something that’s not a zip, perhaps a series of 7zip .7z.001, .002, etc. (from this SO):

& $env:ProgramFiles\7-Zip\7z.exe x .\Downloads\*.7z.* "-o.\Downloads" -y
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curl/wget

This blog covers options for downloading files. While BITS via Start-BitsTransfer is a great option for Windows, Invoke-WebRequest works best for multi-platform scripts:

# wget; Http GET
Invoke-WebRequest https://sh.rustup.rs -OutFile rustup-init.sh
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Visual Studio

If you use Visual Studio you’re familiar with the “developer command prompt”- a cmd shell to use VS executables from the command line. A recent VS 2019 update came with “Developer PowerShell for VS 2019”:

After launching powershell it initializes the environment with:

Import-Module "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\Tools\Microsoft.VisualStudio.DevShell.dll"
Enter-VsDevShell 20a49f0c
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Let’s take a look at Enter-VsDevShell:

PS> Get-Help Enter-VsDevShell

NAME
    Enter-VsDevShell

SYNTAX
    Enter-VsDevShell -VsInstallPath <string> [-SkipExistingEnvironmentVariables] [-StartInPath <string>] [-DevCmdArguments <string>] [-DevCmdDebugLevel {None | Basic | Detailed | Trace}] [-SkipAutomaticLocation] [-SetDefaultWindowTitle] [<CommonParameters>]

    Enter-VsDevShell [-VsInstanceId] <string> [-SkipExistingEnvironmentVariables] [-StartInPath <string>] [-DevCmdArguments <string>] [-DevCmdDebugLevel {None | Basic | Detailed | Trace}] [-SkipAutomaticLocation] [-SetDefaultWindowTitle] [<CommonParameters>]

    Enter-VsDevShell [-Test] [-DevCmdDebugLevel {None | Basic | Detailed | Trace}] [<CommonParameters>]
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For example, to get a powershell instance for VS 2019 Community edition:

$vspath = "C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\"
Import-Module "$vspath\Common7\Tools\Microsoft.VisualStudio.DevShell.dll"
Enter-VsDevShell -VsInstallPath $vspath
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