unix

# Unix & Linux — Command Reference Covers: **File Operations · Process Management · Text Processing · Networking · Scripting · System Administration** ----- ## File System Operations ### File Navigation and Listing The Unix file system follows a hierarchical tree structure with the root directory "/" at the top. Understanding how to navigate this structure efficiently is fundamental to working with Unix systems. Modern Unix systems maintain a consistent directory structure following the Filesystem Hierarchy Standard (FHS). Common directories include: /bin for essential binaries, /etc for system configuration, /home for user directories, /var for variable data like logs, /tmp for temporary files, /usr for user programs, and /proc for process information. ```bash # Basic navigation cd /home/user/projects # Change directory cd ~ # Go to home directory cd - # Go to previous directory pwd # Print working directory ls # List files ls -la # List all files with details ls -lh # Human-readable file sizes ls -lt # Sort by modification time ls -lS # Sort by file size ls -R # Recursive listing ls -1 # One file per line ls -d */ # List directories only # Using ls with various options ls -a # Show hidden files (starting with .) ls -A # Show hidden files except . and .. ls -F # Append file type indicators (* / @ |) ls --color=auto # Colorize output by type # Advanced listing ls -l | grep '^d' # List directories only ls -l | awk '{print $9}' # List just filenames ls -t | head -n 10 # 10 most recently modified files find . -type f -ls # Detailed listing with find ``` ### File Creation and Manipulation ```bash # Create files touch newfile.txt # Create empty file touch -t 202312251200 file # Create with specific timestamp echo "content" > file.txt # Create with content (overwrite) echo "content" >> file.txt # Append content printf "Line1\nLine2\n" > f # Create with newlines cat > file.txt << EOF # Here-document creation Multi-line content here