Cheatsheets
Basics of Using the Command Line

Basics of Using the Command Line

How to Navigate the File System

Show Current Location with pwd

The command 'pwd' shows you the full path to your current location in the file system. It's like asking, 'Where am I?' and getting a full address.

                                
$ pwd
/Users/yourname/Downloads

Create a New Folder with mkdir

The command 'mkdir' creates a new folder. You can specify the name of the new folder. If you give a path, it creates the folder there; otherwise, it creates it where you are now.

                                
$ mkdir my-new-folder
$ ls
Documents    my-new-folder

List Files and Folders with ls

The command 'ls' lists all files and folders in the current directory. If you provide a folder name, it lists contents inside that folder.

                                
$ ls
Documents   Downloads   Pictures

Change Folders with cd

The command 'cd' changes your location to a different folder. For example, 'cd folder-name' moves you into a folder, and 'cd ..' moves you up one level.

                                
$ cd Documents
$ cd ..

Understanding Filesystem Layout

A filesystem is how a computer organizes its files and folders. It’s structured like a tree, with the root at the base and branches representing folders and files.

                                
Root
├── Folder1
│   ├── File1
│   └── File2
└── Folder2

Create a New File with touch

The 'touch' command creates a new, empty file in the current location.

                                
$ touch new-file.txt
$ ls
new-file.txt

What is the Command Line?

The command line, also known as a terminal, is a text-based interface that allows you to interact with your computer’s operating system by typing commands.

Useful Helper Commands

Commands like 'pwd', 'cd', 'ls', and 'mkdir' are useful to navigate and manage files on your computer through the command line interface.

How to View and Change Files and Directories

Copy Files with cp

The 'cp' command copies files or folders from one location to another. The format is 'cp source destination'.

                                
$ cp file1.txt backup/file1.txt

Understanding Command Options

Command options modify the behavior of commands. For instance, 'ls -a' shows all files, including hidden ones, in a directory.

                                
$ ls -a
.   ..   .hiddenfile   file1.txt

Move Files with mv

The 'mv' command moves or renames files or folders. For example, 'mv oldname.txt newname.txt' renames a file, and 'mv file.txt folder/' moves it to a different folder.

                                
$ mv document.txt archive/document.txt

Delete Files with rm

The 'rm' command deletes files. To delete folders and their contents, use 'rm -r'. Be careful, as deleted files cannot be easily recovered.

                                
$ rm unwantedfile.txt
$ rm -r old-folder

Advanced ls Options

The 'ls' command can be combined with various options to display files in different formats. For example, 'ls -l' shows detailed information about each file.

                                
$ ls -l
-rw-r--r-- 1 user user  0 Sep  2 12:34 file.txt

How to Redirect Output and Input

Appending Output with >>

The '>>' command appends the output of a command to the end of a file. For example, 'echo Hello >> file.txt' adds 'Hello' to the end of 'file.txt'.

                                
$ echo "Hello again!" >> greetings.txt

Connecting Commands with | (Pipe)

The pipe '|' takes the output of one command and uses it as input for another. For example, 'ls | grep txt' lists all files ending with '.txt'.

                                
$ ls | grep txt
file1.txt
file2.txt

Redirecting Output with >

The '>' symbol redirects the output of a command to a file, overwriting its contents. For example, 'echo Hello > file.txt' will replace all content in 'file.txt' with 'Hello'.

                                
$ echo "New content" > file.txt

Display File Contents with cat

The 'cat' command displays the content of one or more files directly to the terminal screen.

                                
$ cat notes.txt

Search Inside Files with grep

The 'grep' command searches for specific text in files. For example, 'grep error log.txt' will show all lines in 'log.txt' that contain 'error'.

                                
$ grep "error" logfile.txt

Case-Insensitive Search with grep -i

The 'grep -i' command searches for text, ignoring case. For example, 'grep -i hello greetings.txt' will find 'Hello', 'HELLO', 'hello', etc.

                                
$ grep -i "hello" greetings.txt

Recursive Search with grep -R

The 'grep -R' command searches through all files in a directory and its subdirectories for a specific text.

                                
$ grep -R "function" /my-project

Understanding Output Redirection

Redirecting allows you to send the output of commands to files or other commands, making your command line usage more flexible and powerful.

Setting Up Your Command Line Environment

What is the Command Line Environment?

The command line environment refers to the settings and preferences that affect how the terminal behaves, such as shortcuts, greetings, and environment variables.

                                
$ export PATH="/usr/local/bin:$PATH"

Check Environment Variables with env

The 'env' command lists all environment variables that are currently set in your terminal session. This is useful for debugging and configuring your environment.

                                
$ env
HOME=/Users/yourname
SHELL=/bin/bash

Creating Shortcuts with alias

The 'alias' command allows you to create shortcuts for longer commands. For example, 'alias ll="ls -la"' makes 'll' a shortcut for 'ls -la'.

                                
$ alias ll="ls -la"

Understanding Environment Variables

Environment variables are used to store information that can be used by multiple commands. For example, 'HOME' stores the path to your home directory.

Apply Changes with source

After making changes to configuration files like ~/.bash_profile, use the 'source' command to apply those changes to the current terminal session.

                                
$ source ~/.bash_profile

Review Your Command History with history

The 'history' command displays a list of all commands you’ve entered in the current terminal session. This can be helpful for repeating previous commands.

                                
$ history
1  ls
2  cd Documents
3  mkdir new-folder

Make Variables Available with export

The 'export' command makes a variable available to all child sessions of the terminal. This is often used to set environment variables.

                                
$ export USERNAME="yourname"

Access Home Directory with HOME Variable

The 'HOME' variable stores the path to your home directory. You can use it to quickly navigate back to your home directory.

                                
$ cd $HOME

Programming Cheatsheets: Quick Reference for Productivity

Welcome to our comprehensive collection of programming language cheatsheets! Whether you're a seasoned developer or a beginner, these quick reference guides provide essential tips and key information for all major languages. They focus on core concepts, commands, and functions—designed to enhance your efficiency and productivity.

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