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The PowerShell `CRUD` operations explained

#webdev #beginners #powershell

Table of Contents

Overview

In programming, CRUD is an acronym that stands for CREATE, READ, UPDATE, and DELETE. These are the major operations which are performed by databases.

In this article, we will be looking at how we can implement the basic command line operations (creating or deleting files/folders) in PowerShell using the CRUD concept.

CRUD - Create, Read, Update, Delete

Before we begin, in the following tables, you will see 4 columns:

Alias Alternatives Command Description
cd chdir Set-Location Change directory

which means:

  • Alias - a shorter version of the command
  • Alternatives - alternative versions to alias
  • Command - the full command
  • Description - a brief description of what the command does

With that out of the way, let's get started!

Create

Alias Alternatives Command Description
ni - New-Item Create a file
md mkdir New-Item Create a directory

Officially, the New-Item command is used to create both a file or a directory. That said, as a lazy programmer, ni and md are my go-to commands for doing the same, but faster.

When you need to create a file/folder in the current directory, use a dot (.) as the path, or don't specify the -Path parameter at all.

# short version
C:\> ni "test.txt"

# long version
C:\> New-Item -Path . -Name "test.txt" -ItemType "file"
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If you want to go with the New-Item method, you need to specify the -Path, -Name, and -ItemType parameters. Note that the -ItemType accepts 2 values: file and directory.

C:\> New-Item -Path "C:\root\Documents" -Name "fileName.txt | folderName" -ItemType "file | directory"
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Read

Alias Alternatives Command Description
ii iex Invoke-Item Open a file/folder
start saps Start-Process Open a file/folder
ls gci, dir Get-ChildItem List files and folders
cat - Get-Content Read a file

Invoke-Item vs Start-Process

While the both commands act almost the same, there is a slight difference between them.

  • Invoke-Item - performs the default action specified by the file type
  • Start-Process - opens the executable file with the default application

Basically, you will use the Invoke-Item command to open a file, and the Start-Process to run a command. However, if you want to dive deeper into each command, you can read the following articles:

A quick example of how to use them:

# Invoke-Item
C:\> ii "test.txt"

# Start-Process
C:\> start "test.exe"
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If you try to change the extension of the file, you will see that the command will still work, becuase of either the default action or the default application specified.

# Invoke-Item
C:\> ii "test.exe"

# Start-Process
C:\> start "test.txt"
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Get-ChildItem

The Get-ChildItem (or ls) command is used to list all the files and folders in the current directory. You can also provide a path to the -Path parameter to list the files and folders in a different directory.

C:\> ls

    Directory: C:\root

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
-a----         1/1/2021   1:00 AM              14 test.txt
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Get-Content

The Get-Content command is used to read a file and show what's inside.

C:\> cat "C:\root\test.txt"
Hello, World!
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Update

Alias Alternatives Command Description
cd chdir Set-Location Change directory
ren rename, rni Rename-Item Rename files and folders
cp - Copy-Item Copy files and folders
mv mi, move Move-Item Move files and folders

cd

For me, the cd is the most used command. It's used to move between directories.

  • to go back to parent directory, use cd ..
  • to go to the root directory, use cd \ or cd /
  • to go to a specific directory, use cd "C:\path\"
  • to go to the D drive, use D: or cd D:
  • to go to the current directory, use cd . (I don't know why you would want to do that even though you are already there). 
C:\> cd "root"
C:\root> cd "Documents"
C:\root\Documents> cd ..
C:\root> D:
D:\> cd "projects"
D:\projects> cd C:
C:\root>
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Notice that when you move to the D drive while being in the C:\root\ directory and come back to the C drive, you will be still in the previous directory you were in (C:\root\), not in the root directory (C:\). Because when moving to another drive, the current directory in the previous drive will be saved, which can come very handy in most cases.

ren

The ren or Rename-Item command, as you might have guessed, is used to rename a file or a folder. You can also use the rename or rni aliases.

THe ren command takes 2 parameters: -Path and -NewName. You can either use them or omit them and just provide the path and the new name.

# long version
C:\> ren -Path "C:\root\old.txt" -NewName "next.txt"

# short version
C:\> ren "C:\root\old.txt" "next.txt"
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cp and mv

The cp and mv commands are used to copy and move files and folders. They both take 2 parameters: -Path and -Destination.

C:\> cp -Path "C:\root\old.txt" -Destination "C:\root\new.txt"
C:\> mv -Path "C:\root\old.txt" -Destination "C:\root\new.txt"
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Just like the ren command, you can omit the -Path and -Destination parameters.

C:\> cp "old.txt" "new.txt"
C:\> mv "old.txt" "new.txt"
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Note: When moving a file and providing the new file name instead of folder name, the file will be renamed. It is true for the cp command as well.

Delete

Alias Alternatives Command Description
rm del, erase, ri Remove-Item Remove files and folders
rmdir - Remove-Item Remove a directory
cli clc Clear-Item Clear the content of a file

rm

The rm command is used to delete many different types of items, including files, folders, registry keys, variables, aliases, and functions.

Let's see some examples:

Delete everything in the directory:

C:\> rm "C:\root\examples\*"
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Delete only files with an extension name .txt:

C:\> rm "C:\root\examples\*.txt"
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Delete everything except the .txt files:

C:\> rm "C:\root\examples\*.*" -Exclude "*.txt"
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There are many more cool examples which you can find in the official documentation.

cli

The cli command clears the content of a file. It won't delete the file, but rather remove everything inside of it.

# get the content
C:\> cat "C:\root\test.txt"
Hello, World!

# clear the content
C:\> cli "C:\root\test.txt"

# get the content again
C:\> cat "C:\root\test.txt"
C:\>
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Conclusion

In this article, we have covered the essential basic commands with the CRUD concept in mind. I hope you have learned something new and useful. If you have any questions or suggestions, feel free to leave a comment below. Thanks for reading!

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