PowerShell on Linux - Mini Project: Build & Apply

PowerShell on Linux: Basic File Info Script

📖 Scenario: You are using PowerShell on a Linux system to check details about files in a directory. This is useful when you want to quickly see file names and sizes without switching to other tools.

🎯 Goal: Create a PowerShell script that lists files in a directory and shows their names and sizes in bytes.

📋 What You'll Learn

Create a variable with a directory path

Create a variable to hold a file size limit

Use a loop to get files and filter by size

Print the file name and size for each filtered file

💡 Why This Matters

🌍 Real World

This script helps Linux users who use PowerShell to quickly find small files in a directory, useful for managing disk space or checking file details.

💼 Career

Knowing how to use PowerShell on Linux is valuable for system administrators and developers working in mixed environments or automating tasks across platforms.

1

Set the directory path

Create a variable called $directory and set it to the string "/usr/bin".

PowerShell

$directory = "/usr/bin"
# Your code here

Hint

Use = to assign the string "/usr/bin" to the variable $directory.

2

Set the file size limit

Create a variable called $sizeLimit and set it to the number 10000 (this means 10,000 bytes).

PowerShell

$directory = "/usr/bin"
$sizeLimit = 10000
# Your code here

Hint

Assign the number 10000 to the variable $sizeLimit.

3

Get files and filter by size

Use Get-ChildItem with the path $directory to get files. Use a foreach loop with variable $file to check each file's Length. Inside the loop, use an if statement to select files where $file.Length -lt $sizeLimit. For these files, create a new object with properties Name and Length and add it to a list called $smallFiles.

PowerShell

$directory = "/usr/bin"
$sizeLimit = 10000
$smallFiles = @()
foreach ($file in Get-ChildItem -Path $directory) {
    # Your code here
}

Hint

Start with an empty array $smallFiles = @(). Loop over files with foreach ($file in Get-ChildItem -Path $directory). Use if ($file.Length -lt $sizeLimit) to filter. Add matching files as custom objects to $smallFiles.

4

Display the filtered files

Use foreach with variable $item to loop over $smallFiles. Inside the loop, use Write-Output to print the file name and size in this format: "File: {Name}, Size: {Length} bytes".

PowerShell

$directory = "/usr/bin"
$sizeLimit = 10000
$smallFiles = @()
foreach ($file in Get-ChildItem -Path $directory) {
    if ($file.Length -lt $sizeLimit) {
        $smallFiles += [PSCustomObject]@{Name = $file.Name; Length = $file.Length}
    }
}
foreach ($item in $smallFiles) {
    # Your code here
}

Hint

Loop over $smallFiles and print each file's name and size using Write-Output with string interpolation.

Practice

1. What command do you use to start PowerShell on a Linux system?

easy

A. pwsh

B. powershell.exe

C. start-ps

D. shellps

Solution

1. Step 1: Recall the PowerShell start command on Linux

   On Linux, PowerShell is started by typing pwsh in the terminal.

2. Step 2: Compare options with the known command

   powershell.exe, start-ps, and shellps are not valid commands to start PowerShell on Linux.

3. Final Answer:

   pwsh -> Option A

4. Quick Check:

   PowerShell start command on Linux = pwsh [OK]

Hint: Remember: 'pwsh' starts PowerShell on Linux terminals [OK]

Common Mistakes:

• Typing 'powershell.exe' which is for Windows only
• Using 'start-ps' which is not a valid command
• Confusing shell names

2. Which of the following is the correct syntax to run a Linux command inside PowerShell on Linux?

easy

A. Run-Command 'ls -l'

B. Invoke-Linux ls -l

C. ls -l

D. Start-Linux ls -l

Solution

1. Step 1: Understand how Linux commands run in PowerShell on Linux

   PowerShell on Linux allows running Linux commands directly by typing them as is, like ls -l.

2. Step 2: Evaluate each option

   Invoke-Linux ls -l, Run-Command 'ls -l', and Start-Linux ls -l are not valid syntax to run Linux commands.

3. Final Answer:

   ls -l -> Option C

4. Quick Check:

   Run Linux commands directly in PowerShell = ls -l [OK]

Hint: Run Linux commands directly without extra syntax in PowerShell [OK]

Common Mistakes:

• Adding unnecessary PowerShell cmdlets before Linux commands
• Using quotes incorrectly around Linux commands
• Assuming Linux commands need special wrappers

3. What will be the output of this PowerShell on Linux command sequence?

pwsh
$files = ls /etc | Where-Object { $_.Name -like '*.conf' }
$files.Count

medium

A. Always zero because filtering is incorrect

B. An error because ls is not recognized

C. The list of all files in /etc

D. The number of files in /etc ending with .conf

Solution

1. Step 1: Understand the command sequence

   The command ls /etc lists files in /etc. The Where-Object filters files whose names end with '.conf'.

2. Step 2: Determine the output of $files.Count

   $files stores the filtered list, so $files.Count returns the number of such files.

3. Final Answer:

   The number of files in /etc ending with .conf -> Option D

4. Quick Check:

   Count filtered files = number [OK]

Hint: Count filtered files with .Count property after Where-Object [OK]

Common Mistakes:

• Thinking ls is not recognized in PowerShell on Linux
• Assuming filtering syntax is invalid
• Confusing output with file list instead of count

4. You run this script in PowerShell on Linux:

pwsh
$process = Get-Process -Name "bash"
Write-Output $process.Id

But it returns an error: "Get-Process: The term 'Get-Process' is not recognized." What is the likely cause?

medium

A. PowerShell is not installed correctly on Linux

B. You are running the script in the Linux shell, not inside PowerShell

C. The process 'bash' does not exist

D. Get-Process cmdlet is not available on Linux PowerShell

Solution

1. Step 1: Analyze the error message

   The error says 'Get-Process' is not recognized, which usually means the command is run outside PowerShell.

2. Step 2: Understand environment context

   If you run PowerShell commands in the Linux shell (bash), they won't work. You must be inside PowerShell (started with pwsh) to run Get-Process.

3. Final Answer:

   You are running the script in the Linux shell, not inside PowerShell -> Option B

4. Quick Check:

   Run PowerShell cmdlets inside pwsh shell [OK]

Hint: Run PowerShell commands only inside pwsh shell, not bash [OK]

Common Mistakes:

• Assuming Get-Process is missing on Linux PowerShell
• Thinking the process 'bash' does not exist
• Not starting PowerShell before running commands

5. You want to write a PowerShell script on Linux that lists all running processes and filters only those owned by the current user. Which approach is correct?

hard

A. Get-Process | Where-Object { $_.UserName -eq $env:USER }

B. ps -u $USER | pwsh

C. Get-Process | Where-Object { $_.UserName -eq (whoami) }

D. Get-Process | Where-Object { $_.UserName -eq $env:USERNAME }

Solution

1. Step 1: Identify environment variable for current user in PowerShell on Linux

   PowerShell on Linux uses $env:USER to get the current user's name.

2. Step 2: Check filtering syntax for processes

   Filtering processes by Where-Object { $_.UserName -eq $env:USER } correctly compares the process owner to the current user.

3. Step 3: Evaluate other options

   ps -u $USER | pwsh mixes Linux command with PowerShell incorrectly. Get-Process | Where-Object { $_.UserName -eq (whoami) } uses command output that may not match precisely. Get-Process | Where-Object { $_.UserName -eq $env:USERNAME } uses $env:USERNAME which is typically not set on Linux.

4. Final Answer:

   Get-Process | Where-Object { $_.UserName -eq $env:USER } -> Option A

5. Quick Check:

   Use $env:USER for current user in PowerShell on Linux [OK]

Hint: Use $env:USER to get current user in PowerShell on Linux [OK]

Common Mistakes:

• Using $env:USERNAME which isn't set on Linux PowerShell
• Mixing Linux commands like 'ps -u $USER' with PowerShell incorrectly
• Using command output like (whoami) without precise matching