Windows

PowerShell

Misc

  • Docs, Sample Scripts
  • Use Get-Help <cmdlet-name> to access help information for specific cmdlets.
  • Check version: $PSVersionTable
    • For a breakdown of the version number (e.g. build, revison, etc.): $PSVersionTable.PSVersion
  • Update to latest stable version: github
  • Comments: # comment
  • Clear terminal: clear or cls or Clear-Host
  • Run Powershell Script: .\my-script.ps1
    • Before you’ll be able to run a (first?) script, you need to open PowerShell as administrator and execute this command: Set-ExecutionPolicy RemoteSigned
  • Single Wildcard: ?
    • Example: Matching for am? would give you files named “amy” “amd” and “am3.”
  • VS Code Shortcuts
    • Run selected PowerShell code in current terminal using F8
    • Launch online help for the symbol under the cursor using Ctrl + F1
  • Create a symlink

    • Allows users to control personal environments on a shared server without needing administrative access to change environment variables or make changes to configurations.

      • For shared projects, use git branches.

    • Hard Link:

      • Points directly to the data on the disk.
      • Both the original file and the hard link are indistinguishable; deleting the original file doesn’t affect the hard link, and vice versa.
      • Hard links can only be created within the same filesystem.

    • Symlink (Symbolic Link):

      • Points to the path of another file or directory.
      • If the original file is deleted, the symlink becomes “broken” or “dangling” because it still points to the old, now non-existent path.
      • Symlinks can span across different filesystems and can link to directories.

    • In cmd

      # directory
mklink /D C:\Users\User1\R-current C:\R\R-4.0.5
mklink /D C:\Users\User1\R-lib C:\Users\User1\Documents\R\win-library\4.1

# file
mklink C:\Users\User1\Documents\.Rprofile C:\SharedConfigs\User1.Rprofile

      • R-current is the location of the symlink and C:\R\R-4.0.05 is what the symlink is linking too.

      • Removing \D means you want to link files instead of directories.

      • Should be the same for Linux

      • The symlinks then get added to environment variables in the user’s .Renviron

        R_HOME=C:/Users/User1/R-current
R_LIBS_USER=C:/Users/User1/R-lib

      • The user (User1) connects to the server and launches RStudio. RStudio uses the configuration and paths defined in User1’s environment (.Renviron).

    • In Powershell

      New-Item -ItemType SymbolicLink -Path "C:\Users\User1\R-current" -Target "C:\R\R-4.0.5"

Loops

Iterables

  • Arrays : $folders = @('C:\Folder','C:\Program Files\Folder2','C:\Folder3')

  • $_ (Docs)

    • Automatic Variable; Alias for $PSItem
      • Docs for automatic variables
    • Useful for looping through objects in a directory. See “Change Name (or Extensions) of Multiple Files” for an example of usage
    • Get the properties of an object

      • Example: Using Get-ItemProperty (Docs)

        Get-ItemProperty scrapsheet.txt | Format-List
        • Property names will be on the left side of the output

      • Example: Using Get-Member (Docs)

         Get-ChildItem *.txt | Select-Object -First 1 | Get-Member
        • Selects the first text file in the directory and gets the Properties and a bunch of other stuff like methods which also can be used with $_
        • Descriptions are awful for a lot of the stuff, but for the most part, you can guess what the property is.
    • Some properties that can be used with $_
      • File System Objects:
        • .Name: Returns the name component of a file
        • .FullName: Returns the full path of the file.
        • .Length: Returns the size of the file in bytes.
        • .CreationTime: Returns the date and time the file was created.
        • .LastWriteTime: Returns the date and time the file was last modified.
        • .IsReadOnly: Returns $true if the file is read-only, $false otherwise.
      • Process Objects:
        • .Id: Returns the unique identifier (PID) of the process.
        • .Name: Returns the name of the process.
        • .MainWindowTitle: Returns the title of the process’s main window (if applicable).
        • .WorkingDirectory: Returns the working directory of the process.
        • .CPU: Returns the CPU usage of the process.
      • Registry Objects:
        • .Name: Returns the name of the registry key.
        • .Hive: Returns the hive of the registry key (e.g., HKLM, HKCU).
        • .Value: Returns the value of the registry key (if applicable).
        • .Path: Returns the full path of the registry key.

Foreach

  • Uses a typical for-loop structure

  • See Snippets for an example of iterating over the output of Get-ChildItem

  • Iterate over an array

    # Create an array of folders
$folders = @('C:\Folder','C:\Program Files\Folder2','C:\Folder3')

# Perform iteration to create the same file in each folder
foreach ($i in $folders) {
    Add-Content -Path "$i\SampleFile.txt" -Value "This is the content of the file"
}
    • $i is the for-loop variable and $folders is the iterable
    • Add-Content creates a text file in each of the folders in the array.

ForEach-Object

  • Similar to {purrr::map}

  • Iterable is piped into ForEach-Object

    $folders = @('C:\Folder','C:\Program Files\Folder2','C:\Folder3')
$folders | ForEach-Object (Add-Content -Path "$_\SampleFile.txt" -Value "This is the content of the file")
    • Does the same thing as the first example in the Foreach section
    • Add-Content creates a text file in each of the folders in the array.
    • $_ is the for-loop variable — called an “automatic variable.” See Iterables section.

  • Example: Generate Multiple Files

    # Create a directory for the output files
New-Item -ItemType Directory -Path "output" -Force

# Loop through numbers 0 to 9 and create empty files
0..9 | ForEach-Object {
    $fileName = "output/sample_{0:D3}.txt" -f $_
    New-Item -ItemType File -Path $fileName
}

Write-Host "Files created in the output directory."

    • {0.D3} says use 3 digits and make sure there leading zeros for single or double digit numbers

    • Files that get created

      output/sample_000.txt
output/sample_001.txt
output/sample_002.txt
...

ForEach Method

  • Similar to using Pyhon’s apply on an iterable.

  • Method applied an array

    $folders = @('C:\Folder','C:\Program Files\Folder2','C:\Folder3')
$folders.ForEach({
    Add-Content -Path "$_\SampleFile.txt" -Value "This is the content of the file"
})
    • Does the same thing as the first example in the Foreach section
    • Add-Content creates a text file in each of the folders in the array.
    • $_ is the for-loop variable — called an “automatic variable.” See Iterables section.

Commands

  • Subsetting

    • Example: Get size of the third item

      $x = dir # like ls but has directory/file sizes
$x[2].Length # 0-indexed; Length is file size in bytes

  • Change directories

     Set-Location "Documents\R\Projects"

  • Create a New Folder

     New-Item -ItemType Directory -Path "Folder Name"
    • Assumes you’re already in the directory that you want the folder in. You can also use a path, e.g. "C:\Temp\Documents\New Folder\Subfolder1\\Subfolder2".
    • -Force can be added at the end to ensure that the directory is created even if a directory with the same name already exists in the current location.
      • Without it, powershell will throw an error if it already exists
      • Commonly used when you want to perform an operation that might overwrite or replace existing data, and you want to suppress any confirmation prompts or errors that might occur.

  • Change Name of File

    Rename-Item -Path "c:\logfiles\daily_file.txt" -NewName "monday_file.txt"

  • Change Name (or Extensions) of Multiple Files

    Get-ChildItem *.md | Rename-Item -NewName { $_.Name -replace '.md','.qmd' }
    • Get-ChildItem: cmdlet gets all the files in the current folder that have a .mc file extension
    • Results piped to Rename-Item
      • NewName: Has a value that’s a script block that runs before the value is submitted to the NewName parameter.
        • $_: (automatic variable) It represents each file object as it comes to the command through the pipeline.
        • -replace: Operator replaces the file extension of each file with .qmd.
          • Notice that matching using the -replace operator is not case sensitive.

  • Execute a File

    Invoke-Item configuration.cmd

  • Multi-line Commands

    ffmpeg -i input.mkv -map 0:v:0 `
       -map 0:a:2 -map 0:a:0 -map 0:a:1 -map 0:a:3 `
       -map 0:s -c copy `
       -disposition:a:0 default `
       reordered.mkv

    • In bash, it’s a backslash (\), but in Powershell, it’s a backtick ( ` )

    • *Don’t forget that there’s a space between the last character and the backtick.*

    • In practice, this will look like

      ffmpeg -i .input.mkv -map 0:v:0 `
>> -map 0:a:2 -map 0:a:0 -map 0:a:1 -map 0:a:3 `
>> -map 0:s -c copy `
>> -disposition:a:0 default `
>> reordered.mkv

  • String Matching

    • Print line with pattern

      Select-String -Path "file*.txt" -Pattern "error"
file1.txt:3:This is the error line of the file
file2.txt:3:This is the error line of the file
file3.txt:3:This is the error line of the file
      • Matches the 3rd line of each file

  • Get stats on a process

    Get-Process -Name chrome
    • Handles: The number of handles that the process has opened.
    • NPM(K): The amount of non-paged memory that the process is using, in kilobytes.
    • PM(K): The amount of pageable memory that the process is using, in kilobytes.
    • WS(K): The size of the working set of the process, in kilobytes. The working set consists of the pages of memory that were recently referenced by the process.
    • VM(M): The amount of virtual memory that the process is using, in megabytes. Virtual memory includes storage in the paging files on disk.
    • CPU(s): The amount of processor time that the process has used on all processors, in seconds.
    • ID: The process ID (PID) of the process.
    • ProcessName: The name of the process. For explanations of the concepts related to processes, see the Glossary in Help and Support Center and the Help for Task Manager.

  • Variables

    • Docs

    • Types

      $a = 12                         # System.Int32
$a = "Word"                     # System.String
$a = 12, "Word"                 # array of System.Int32, System.String
$a = Get-ChildItem C:\Windows   # FileInfo and DirectoryInfo types

    • Clear variable value

      Clear-Variable -Name <variable_name>

    • Delete Variable

      Remove-Item -Name <variable_name>

    • Change format

      [datetime] $dates = "09/12/91"
      • From string to datetime

  • Environment Variables

    • Docs

    • Create an environment variabl

      New-Item -Path Env:\Foo -Value 'Bar'
      • Foo environment variable with a value of Bar

    • Set an environment variable

      Set-Item -Name PYTHONSTARTUP -Value C:\path\to\pythonstartup.py

      • Same expression to modify existing environment variable

      • Or

        $Env:QUARTO_DENO_EXTRA_OPTIONS = "--v8-flags=--max-old-space-size=8192"

    • Delete environment variable

      Remove-Item -Path Env:\Foo* -Verbose

    • Verify value of an environment variable

      $Env:<variable_name>

  • Ports

    • Find application using a port.

      netstat -aon | findstr ':80'
netstat -anp | find ":80"
      • If port 80 is being used by the application, it will return a PID. Then you can find it in Task Manager >> Processess

    • List all Listening and Established ports

      netstat -anob

    • Check for processes using a port

      Get-Process -Id (Get-NetTCPConnection -LocalPort 80).OwningProcess

    • Test connection to local port to see if it’s open

      Test-NetConnection -ComputerName localhost -Port 80 | Select-Object TcpTestSucceeded

    • Check firewall settings for an app

      netsh advfirewall firewall show rule name="name_of_app"

Snippets

  • Example: Read in name of servers and ping each of them

    $servers = Get-Content .\servers.txt

foreach ($server in $servers) {
    try {
        $null = Test-Connection -ComputerName $server -Count 1 -ErrorAction STOP
        Write-Output "$server - OK"
    }
    catch {
        Write-Output "$server - $($_.Exception.Message)"
    }
}
    • Get-Content reads the server names from each line in the the server.txt file
    • foreach iterates through the server names
    • try tests the connection and catch outputs an error message if a server fails.
    • If Test-Connection fails the error message is stored in the $null variable
    • The error message line has an interesting syntax
      • $_ is an automatic variable that represents $null which contains the error message which is selected by .Exception-Message.
      • $() evaluates the expression

  • Example: Take files from a directory and iterate them as inputs to a function.

    $directory = "C:\Users\me\Documents\AnyCap Screen Recorder"

# Define the FFmpeg command
$ffmpegCommand = '-i {0} ' +
                 '-c:v libx265 ' +
                 '-crf 28 ' +
                 '-preset medium ' +
                 '-vf scale=-1:720 ' +
                 '-c:a copy ' +
                 'C:\Users\me\Documents\temp-storage\{1}'

# Get all files in the directory
$files = Get-ChildItem -Path $directory `
                       -Filter "*.mp4" 

# Loop through each file and apply the FFmpeg command
foreach ($file in $files) {
  # Construct the full command with the current file path
  $fullCommand = $ffmpegCommand -f "`"$($file.FullName)`"", $file.Name
  # Execute the FFmpeg command
  Start-Process -FilePath "ffmpeg.exe" `
                -ArgumentList $fullCommand `
                -Wait `
                -NoNewWindow
}

Write-Host "Finished processing files!"

    • $ffmpegCommand variable is a concantenated string using multiple lines for readability. {0} and {1} are placeholders to be filled in later.

      • Note the space included at the end of each argument before the single quote since there’s no space included during concantenation.

    • Get-ChildItem retrieves files from the specified directory ($directory).

      • -Filter filters files that match the pattern (e.g., *.mp4).

    • The foreach loop iterates through each file ($file) in the $files collection.

      • -f flag stands for format. Says to replace {0} and {1} in the $ffmpegCommand template with these properties.

        "`"$($file.FullName)`""
        • Since the directory name has spaces in it, extra quotes must included in order for the path to be quoted within the output string. A quoted file path in necessary forffmpeg to be able to read a directory name with spaces in it.
        • $file.FullName: This is the full path of the current file. It is enclosed in $() to ensure that the property is properly evaluated and its value is included in the string.
          • If there were no spaces in the directory name, then $file.FullName is only thing that would be required. Everything else in this description could be discarded
        • `"$($file.FullName)`": The double quotes "..." are used to create a string literal. Placing the entire expression $($file.FullName) within these double quotes ensures that the value of $file.FullName is treated as a single string, even if it contains spaces or special characters.
          • The backticks are escape characters in PowerShell and indicate that the double quotes should be treated as literal characters and not as operators formatting a string.
        • "`"\$(\$file.FullName)`"": The additional double quotes at the beginning and end are used to format the expression as string for when it’s used as an argument in Start-Process.
        • The resulting path in the ffmpeg argument will look like: "<full file path>".

      • Start-Process launches ffmpeg.exe with the constructed $fullCommand arguments.

        • -Wait ensures the command finishes before continuing.
        • -NoNewWindow says run ffmpeg in the same console window and don’t open a new one.

  • Example: Use a counter to create a hierarchy of file names

    # Define the directory containing the files
$directory = "C:\Users\me\Documents\temp-storage"

# Define the FFmpeg command (replace with your desired command)
$ffmpegCommand = '-i {0} ' +
                 '-f segment -segment_time 4140 ' +
                 '-c copy ' +
                 'C:\Users\me\Documents\temp-storage\output\{1}'

# Get all files in the directory
$files = Get-ChildItem -Path $directory `
                       -Filter "*.mp3" 
$counter = 0
# Loop through each file and apply the FFmpeg command
foreach ($file in $files) {
  $output_file = "Mistborn-02-The-Well-of-Ascension-{0:D2}-" -f $counter + "%02d.mp3"
  # Construct the full command with the current file path
  $fullCommand = $ffmpegCommand -f "`"$($file.FullName)`"", $output_file
  # Execute the FFmpeg command
  Start-Process -FilePath "ffmpeg.exe" `
                -ArgumentList $fullCommand `
                -Wait `
                -NoNewWindow
  $counter++
}

Write-Host "Finished processing files!"
    • Similar to previous example except the ffmpeg expression splits each of the iterated files into multiple files.
    • -f inserts the value of $counter into the string at {0:D2} (2 digits with a leading 0).
      • This is the first level of the hierarchy representing the current file being iterated
    • %02d is specific to ffpmpeg. It tells it to enumerate the file names it creates to have 2 digits with a leading 0.
    • $counter++ adds 1 to the current value of the variable
    • The output has file names like Mistborn-02-The-Well-of-Ascension-02-03.mp3 which is 3rd file that was created from splitting the 2nd iterated file.

Batch Scripting

  • Misc

    • Resources
    • To keep the prompt window open after script execution, place these either of these commands at end of your script.
      • pause: Keeps window open until you press any key.
      • Via timer: e.g. timeout /t 300
      • cmd /k: The prompt will remain active and you can execute additional commands manually.

  • Example: Create variables and execute

    @echo off

rem Set the path to the Rscript executable
set RSCRIPT="C:\Users\user\AppData\Local\Programs\R\R-4.2.3\bin\Rscript.exe"

rem Set the path to the R script to execute
set RSCRIPT_FILE="C:\Users\user\my_r_script.R"

rem Execute the R script
%RSCRIPT% %RSCRIPT_FILE%

rem Pause so the user can see the output
exit
    • @echo off - This line turns off the echoing of commands in the command prompt window, making the output cleaner.
    • rem - Keyword that denotes a comment in a batch file.
    • set RSCRIPT= - This line assigns the path to the Rscript executable to the environment variable RSCRIPT.
    • set RSCRIPT_FILE= - The path to the R script file is assigned to the environment variable RSCRIPT_FILE.
    • %RSCRIPT% %RSCRIPT_FILE% - Executes the R script using the Rscript executable and passes the path to the R script file as an argument.
    • exit - This command exits the batch file and closes the command prompt window.

  • Example: Exit if script errors

    Rscript "C:\Users\ercbk\Documents\R\Projects\Indiana-COVID-19-Tracker\R\collection\build-opentab-dat.R"

REM if the data building script errors, bat script terminates without running other scripts or commands
if %errorlevel% neq 0 exit /b %errorlevel%

cd "C:\Users\ercbk\Documents\R\Projects\Indiana-COVID-19-Tracker"

git add data/YoY_Seated_Diner_Data.csv
git commit -m "opentab data update"
git pull
git push

EXIT

WSL

  • Resources

    • Docs
    • To update password (link) using username

  • Notes from

  • Load Linux: wsl -d Ubuntu-22.04 where -d is for –distribution

  • Stop Linux

    • all distros: wsl shutdown
    • 1 distro: wsl terminate <distro name>

  • Exit linux terminal back to command prompt or powershell: exit

  • WSL Help: wsl --help

  • WSL Version: wsl --version

  • Available Linux Distributions and the version of WSL they’re installed under

    PS C:\Users\tbats> wsl --list --verbose
  NAME            STATE           VERSION
* Ubuntu-22.04    Stopped         2
    • Version 2 says 22.04 is working in WSL 2

  • Uninstall a distribution: wsl --unregister <distro name>

  • Update WSL: wsl --update

    • --web-download: Download the latest update from the GitHub rather than the Microsoft Store.

  • Download apps

    sudo apt install <app>

  • Update Linux Distro

    sudo apt update
sudo apt upgrade

  • WSL Configs:

    • Global config affects all distributions and the Distribution config on affects that particular distribution
    • Global Config: C:\Users\<user name>\.wslconfig
      • Docs
      • The .wslconfig file does not exist by default. It must be created and stored in your %UserProfile% directory to apply these configuration settings.
    • Distribution Config:
      • Docs
      • Type \\wsl.localhost in file explorer path box
        • Or if you know the name of the distribution: \\wsl.localhost\Ubuntu-22.04\etc
        • Creates a Network connection to wsl.localhost
      • Click on the particular distribution
      • Go to etc\wsl.conf

  • Paths

    • Ubuntu mounts the Windows C: drive at /mnt/c/

    • Windows locates the Ubuntu root directory at \wsl.localhost\Ubuntu-22.04

    • Root Paths

      Folder: Ubuntu path (bash): Windows path (PowerShell):
      Ubuntu user directory /home/<linux user name> \wsl.localhost\Ubuntu-22.04\home\<linux user name>
      Windows user directory /mnt/c/Users/<windows user name> C:\Users\<windows user name>

    • Example:

      • Locating the Projects folder on the Linux file system while in Bash, /home/<linux user name>/Projects
      • Locating the Projects folder on the Linux file system while in PowerShell, \wsl.localhost\Ubuntu-22.04\home\<linux user name>\Projects

  • Increase RAM allocation and number of processors

    • Docs

    • Defaults:

      • WSL limits distros to only 50% of your total memory on Windows
      • The same number of logical processors on Windows

    • Setting in .wslconfig

      # Settings apply across all Linux distros running on WSL 2
[wsl2]

# Limits VM memory to use no more than 4 GB, this can be set as whole numbers using GB or MB
memory=4GB 

# Sets the VM to use two virtual processors
processors=2
      • [wsl2] is a section label even though all the settings underneath it aren’t indented. I’m guessing all settings underneath it belong to it until another section heading is encounterd.