learn-co-students / cli-essentials-bash-files-and-directories-dumbo-web-033020

Navigating Files and Directories in Bash

Learning Goals

• List directory files in the shell with ls
• Move or rename files and directories with mv
• Copy Files with cp
• Create empty files with touch
• Make new directories with mkdir
• Remove files with rm

Introduction

In the previous lesson we learned how to "navigate" the directory structure of our file system. But our file systems (and lives) would be so boring without files. Copying files, moving files, reading the contents of files, feeding files to the ruby program, cat .gifs. We looooooove files.

This lesson will show you how to work with your files. In time, you might stop using Finder and other tools because it's so much faster (and fun!) to use the CLI.

List Directory Files in the Shell with ls

In a new terminal, which automatically puts you in your home directory, try this:

$ ls

The command ls stands for "list" — the first character is a lower case letter L. After you run it, you should then see a list of all the files within your working directory.

Note: For Ubuntu/WSL users, your home directory may start out empty, so you might not see anything running ls. If this is the case, try creating a folder. In fact, now is a good time to create a Development folder where you can store your coursework. We'll use mkdir to create the folder (more on this in a moment):

mkdir Development

Once the folder is created, run ls again and you should see Development listed.

True to Unix style the ls command is easy to type and short (both keys on the home row of a keyboard, one letter on one hand the other on the other hand, it's about as fast as it can get; handy for a command we will run all the time).

We can list the contents of another directory by providing an absolute or relative path

$ ls pathname

Using Flags with Commands

We can use flags on most Unix commands to give more specific instructions or to change the output. Most programs accept flags, or options for execution.

A flag is denotated by a - ("dash").

$ ls -l

This prints out a list of all the files with "long form" output: it will tell us details about which user account owns the file, what the permissions for users are on that file, and the file name.

For example:

$ ls  /var/tmp
SIMToolKit
hi
pfwtfp-dice-thrower-from-a-file
sinatra-user-auth

becomes:

$ ls -l /var/tmp
total 0
drwxrwxrwx   3 byron.poodle  wheel   96 Jun  5  2018 SIMToolKit
drwxr-xr-x   2 byron.poodle  wheel   64 Jun  5  2018 hi
drwxr-xr-x  12 byron.poodle  wheel  384 Nov  9 15:35 pfwtfp-dice-thrower-from-a-file
drwxr-xr-x  18 byron.poodle  wheel  576 May 21  2018 sinatra-user-auth

You don't need to know what all those extra bits of information mean now, but realize that flags can really enrich the output you get.

Single-character options can typically be combined with each other. For example, in the ls command, h is an option on the l flag meaning "human readable formats." They can be combined with a meaning "all information" including "hidden files" (files that start with a ., often used for internal operating system configuration — we'll expand on this in a moment).

Try these three together:

$ ls -lah

And also:

$ ls -l -a -h

Both are valid input options and mean the same thing, as far as ls is concerned.

When you entered $ ls -lah above, you should have a received a list of files including some that you hadn't seen from entering just $ ls before:

drwxr-xr-x   6 kellyegreene  staff   204B Jun  2 11:21 .
drwxr-xr-x   5 kellyegreene  staff   170B May 28 15:52 ..
-rw-r--r--@  1 kellyegreene  staff   6.0K May 28 15:52 .DS_Store
drwxr-xr-x  13 kellyegreene  staff   442B Jun  2 11:02 .git
-rw-r--r--   1 kellyegreene  staff    66B May 28 15:49 .learn
-rw-r--r--   1 kellyegreene  staff    11K Jun  2 11:21 README.md

Notice that at the top of the file output there are a bunch of files that start with a ., like .DS_Store

Files like .DS_Store are not listed. That's because files and directories that start with a . are hidden files. Shells are often configured by putting information in these hidden files. We'll not talk about these types of files in this lesson except to say that sometimes things are hidden until you add a flag.

Note: Combining flags is only valid for single-letter options. A "long option" such as --force is defined with more than one character and must be entered with its own flag.

Move or Rename Files and Directories with mv

Move, or mv is a command that moves one or more files or directories from one place to another. To move a file from the current directory to another location, enter a path as the third word on the command line.

$ mv filename ./dir1

We can also rename a file or directory using the mv command. To rename a file with mv, the third word on the command line must end in the new filename.

$ mv original_program.rb renamed_program.rb

We could combine these two usages as:

$ mv temp_download.gif ~/Desktop/cats_with_weapons/ninja_cat.gif

NOTE: Look how we're using the ~ shortcut!

Copy Files with cp

If you think about it, move is really "copy, but delete the original." Well, cp does a mv, but doesn't delete the original. It's therefore a "copy."

It uses the same snytax as mv:

cp letter_to_mom.txt letter_to_mom-2019-02-15.txt

If you want to copy a directory and its file contents, you need to use the -r flag.

cp -r february_cat_gifs ~/Desktop/vital_media_files

NOTE: Look how we're using the ~ shortcut! This expands into /Users/username/Desktop/vital_media_files

Create Empty Files with touch

We can use the touch command to create empty files in the current directory. Try:

$ touch hello_world.rb

Now try:

$ ls

You should see the file you just created, hello_world.rb, in the working directory. Note that this is an empty file and has nothing inside of it, because you just created it.

Make New Directories with mkdir

We can make directories with the mkdir command:

$ mkdir name_of_directory

Now if you enter ls you should see the empty directory you just created in the working directory.

Remove Files with rm

To delete a file, we can enter rm at a shell prompt. Note: Deleting a file with rm is permanent. This action cannot be undone.

$ rm hello_world.rb

Much like cp, if you want to delete a directory, you need to provide the -r flag

$ rm -r ~/Desktop/pokemon_fan_fiction

There are additional options to rm:

• -i (interactive) — Prompts you to confirm the deletion. This option can stop you from deleting a file by mistake.
• -f (force) — Overrides interactive mode and removes the file(s) without prompting. Use this with caution. This action cannot be undone!
• -v (verbose) — Shows the progress of the files as they are being removed.

Conclusion

There are a variety of commands you can use to manipulate files via the command line. If this list seems overwhelming at first, remember that it takes all programmers a little time to practice their CLI workflows. Refer back to these resources as you need to, and it will get easier as you go along.

Resources

• Lifehacker on the Command Line
• Environment Variables
• Built-in Shell Commands Very useful
• 15 Useful Bash Commands
• The One True Path
• More on paths - Wikipedia
• How Dot Files Became Hidden Files