Working with files and folders

Written Explanation

The five jobs and their commands

Notice the pattern: copy, move, and delete name what to act on first, and where to put it second. "Copy this there. Move this there."

Windows PowerShell has no touch command. New-Item creates a file instead. Also, PowerShell aliases such as cp, mv, and rm exist on Windows but may not exist in PowerShell on Linux or macOS, so use the full Copy-Item, Move-Item, and Remove-Item names if an alias is missing.

Making folders: mkdir

$ mkdir sandbox
$ cd sandbox

To make several levels at once, Bash needs the -p ("parents") option:

$ mkdir -p garden/plants/herbs

Without -p, Bash refuses if garden/plants does not exist yet. PowerShell's mkdir creates missing parent folders by default, as far as I know, so mkdir garden/plants/herbs is enough there. If you are unsure, create the folders one level at a time. You can also create several sibling folders in one go by listing them: mkdir src docs.

Making files: touch and New-Item

$ touch notes.txt            # Bash
PS> New-Item notes.txt -ItemType File     # PowerShell

touch on a file that does not exist creates an empty one. On a file that exists it only updates its modification time and leaves the content alone. The file is empty until something writes into it. Lesson 4 shows how to write text into a file with >.

Looking inside a file: cat and Get-Content

$ cat notes.txt
PS> Get-Content notes.txt

Both print the file's text to the screen. cat also works as an alias in PowerShell. For a small file this is a quick check; do not use it on a huge or binary file, since you would flood the terminal.

Copying: cp and Copy-Item

$ cp notes.txt backup.txt         # copy a file under a new name
$ cp notes.txt garden/            # copy into a folder, keeping the name

The original stays where it was. To copy a folder and everything inside it, Bash needs -r ("recursive", meaning "include what is inside"):

$ cp -r garden garden-copy
PS> Copy-Item garden garden-copy -Recurse

If the destination file already exists, a copy may replace it without asking. Bash's cp -i asks first. PowerShell's behavior differs for existing files, so look at what is in the destination first.

Moving and renaming: mv and Move-Item

A move takes the original away from its old place and puts it in the new one. There is only one copy afterwards.

$ mv notes.txt garden/            # move into a folder
$ mv notes.txt ideas.txt          # same folder, new name: a rename

Renaming is moving to a new name. There is no separate rename command in Bash. If the destination is an existing folder, the file goes inside it. If it is a new name, the item is renamed. mv moves folders too, with no -r. PowerShell has Rename-Item as well, but Move-Item works for renames.

Deleting: rm and Remove-Item

$ rm ideas.txt
PS> Remove-Item ideas.txt

Deletion from the terminal is permanent for practical purposes: the file does not go to the recycle bin or trash that you know from the desktop. I did not find that stated on Microsoft's documentation page for Remove-Item, so treat it as the working rule. Assume that nothing you delete here can be brought back.

Folders need extra words:

• rmdir name removes an empty folder only. It is the safest tool.
• rm -r name in Bash deletes a folder and everything inside it.
• Remove-Item name -Recurse is the PowerShell equivalent. Without -Recurse, PowerShell asks you to confirm when the folder has contents. The Microsoft page notes this prompt cannot be silenced with -Confirm:$false.

Wildcards make deletion more dangerous. * means "anything". rm *.log removes every file ending in .log in the current folder. If you are in the wrong folder, you delete the wrong files. Never type rm -r * while unsure of your location.

The safe-delete routine

Before you delete anything, do these three things:

1. pwd. Where am I?
2. ls (or Get-ChildItem). What is here? Is the thing I want to delete listed, and is nothing else about to go with it?
3. Read the command out loud before pressing Enter.

PowerShell offers a preview: add -WhatIf and the command shows what it would do without doing it. Bash's closest help is rm -i, which asks before each deletion. Use them while you are learning.

PS> Remove-Item garden -Recurse -WhatIf

Quoting reminder

Names with spaces still need quotes: rm "old notes.txt". Forgetting them can make the shell treat two words as two files, which is a classic way to delete the wrong thing.