Command-Line Interface (CLI)

File and Directory Commands

Command	Description
ls	List files/folders
ls -a	List all files including hidden
pwd	Show current directory
cd <folder>	Change directory
cd /	Go to root directory
cd or cd ~	Go to home directory
cd ..	Go up one directory
cd -	Go to previous directory
mkdir <folder>	Create directory
touch <file>	Create empty file
rm <file>	Delete file
rm -r <folder>	Remove folder and contents
rmdir <folder>	Remove empty folder

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File Viewing and Editing

Command	Description
cat <file>	Show file contents
cat -n <file>	Show file with line numbers
cat > <file>	Create/overwrite file (input, Ctrl+D to end)
cat >> <file>	Append to file (Ctrl+D to end)
nano <file>	Simple text editor (Ctrl+O save, Ctrl+X exit)
vim <file>	Powerful editor (i insert, Esc, :wq save & exit)

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Permissions and Ownership

Command	Description
ls -l <file>	Show file permissions and details
ls -@l <file>	Show permissions + extended attributes (macOS)
chmod u=rw,g=r,o=r <file>	Change permissions (owner/group/others)
chmod o+rw <file>	Add read/write for others
chown <user> <file>	Change file owner
chgrp <group> <file>	Change file group
sudo chown root <file>	Change owner to root
sudo chgrp root <file>	Change group to root

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Process and System Commands

Command	Description
sudo	Run command as administrator
ps / ps aux	Show running processes
kill <pid>	Stop a process by process ID
top / htop	Interactive process viewer
bg	Send process to background
fg	Bring process to foreground

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Package Managers

Command	OS/Use
apt-get	Linux package manager
brew	macOS package manager
snap	Universal package manager
pip	Python package installer

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Navigation Stack

Command	Description
pushd	Save current dir on stack + switch dir
popd	Return to previous directory on stack