Linux
Special Variables $_ - Last argument of previous command mkdir my_directory && cd "$_" cp file.txt /backup && ls "$_" # ls /backup !! - Repeat last command sudo !! # Run last command with sudo echo "test" && !! # Repeat the echo !$ - Last argument of
Linux
Method 1: Using dpkg-reconfigure (Recommended for Ubuntu/Debian) This is the cleanest and most Ubuntu-appropriate method: Restart the SSH service: sudo systemctl restart ssh Reconfigure OpenSSH server to regenerate keys: sudo dpkg-reconfigure openssh-server Remove existing host keys: sudo rm /etc/ssh/ssh_host_* Method 2: Manual key generation If you
Linux
Table of Contents * What is Flatpak? * Key Features * Installation * Basic Usage * Application Management * Security & Sandboxing * Permission Management * Advanced Features * Troubleshooting * Best Practices What is Flatpak? Flatpak is a universal package management system for Linux distributions that provides a sandboxed environment for running desktop applications. It was developed as an
Linux
Method 1: Using apt-mark hold (Recommended) This is the most common and recommended method: # Hold a specific package sudo apt-mark hold package-name # Hold multiple packages sudo apt-mark hold package1 package2 package3 # Check which packages are held apt-mark showhold # Remove the hold sudo apt-mark unhold package-name Example: sudo apt-mark hold apache2
Linux
Both commands terminate processes but differ in how they identify targets: kill * Requires process ID (PID) * Syntax: kill [options] <PID> * More precise targeting * Example: kill 1234 pkill * Accepts process name patterns * Syntax: pkill [options] <pattern> * Can target multiple processes at once * Example: pkill firefox Key differences:
Linux
awk is a powerful text processing language. Here are some advanced use cases: 1. Advanced Field Processing Input (grades.csv): Alice,Math,85,A,Science Bob,Math,92,A,Arts Charlie,Math,78,B,Science Command: # Calculate average score for students with grade A awk -F',' '$5
Linux
awk is a powerful text processing language. Here are common use cases with examples: Basic Syntax awk 'pattern { action }' input_file 1. Print Specific Columns # Print first and third columns awk '{print $1, $3}' file.txt # Print last column using NF (Number of Fields) awk '
Linux
Introduction awk is a powerful text processing tool for pattern scanning and processing. It's particularly useful for manipulating structured data and generating reports. Basic Structure pattern { action } * Works on input line by line * If pattern matches, execute action * Both pattern and action are optional Common Use Cases 1.
Linux
1. In-place File Editing Edit file directly with backup sed -i.bak 's/foo/bar/g' file.txt Edit without backup (dangerous!) sed -i '' 's/foo/bar/g' file.txt 2. Advanced Regular Expressions Swap first and last characters echo "hello" | sed
Linux
Basic Syntax sed [OPTIONS] 'COMMAND' file.txt 1. Substitution (s command) Replace first occurrence per line: sed 's/apple/orange/' fruits.txt Replace all occurrences (global): sed 's/apple/orange/g' fruits.txt Case-insensitive replacement: sed 's/apple/orange/gi' fruits.txt
Linux
Introduction sed (Stream EDitor) is a powerful text processing tool for: * Parsing and transforming text * Performing substitutions * Filtering content * Non-interactive text editing Basic Syntax sed [options] 'script' inputfile Common Options * -i: Edit files in-place (dangerous but useful) * -E: Use extended regular expressions * -n: Suppress automatic printing * -e: Add
Linux
Basic File Viewing head - View beginning of files head file.txt # Show first 10 lines head -n 5 file.txt # Show first 5 lines head -c 20 file.txt # Show first 20 bytes tail - View end of files tail file.txt # Show last 10 lines tail -n 15