Master Linux Command Line: Essential Tips, Shortcuts, and Powerful Tricks

Safe Deleting Files

Set an alias for rm to request confirmation before deleting, e.g., rm -i. To disable the alias temporarily, use unalias rm or place unalias rm in ~/.bashrc if you prefer the original behavior.

Using sudo

When you forget to prepend sudo, you can repeat the last command with sudo !! or create an alias that includes sudo, for example alias update='sudo apt update'.

Command Editing and Cursor Movement

Useful readline shortcuts include Ctrl+U to delete from the start of the line to the cursor, Ctrl+K to delete from the cursor to the end, Ctrl+A and Ctrl+E to move to the beginning or end of the line, Alt+F / Alt+B to move a word forward or backward, and Ctrl+W to delete the previous word.

History Command Quick Execution

Use !n where n is the command number from history, or !! to repeat the last command.

Real‑time Log Viewing

Watch a log file as it grows with tail -f filename.log. The same effect can be achieved with less +F filename.log.

Disk or Memory Usage

Check mounted filesystem usage with df -h. Inspect memory statistics with free -h, which shows total, used, free, and available memory.

Find Process ID by Name

Retrieve a PID using pgrep hello or pidof hello, where hello is the process name.

Kill Process by Name

Terminate a process directly by name with killall hello or pkill hello.

View Process Runtime

Show how long a process has been running with ps -p 24525 -o lstart,etime, where 24525 is the PID.

Quick Directory Switching

Use cd - to return to the previous directory, cd to go to the home directory, and cd /path && command (or cd /path && rm -rf *) to ensure the second command runs only if the first succeeds.

Multiple Commands Execution

Separate commands with a semicolon ( ;) to run them sequentially regardless of success, or use && to run the second command only if the first succeeds.

View Compressed Log Files

Read a gzipped log without extracting using zcat test.gz or zless test.gz.

Clear File Content

Truncate a file instantly with >filename.

Log to File and Console

Redirect script output to both a log file and the console with ./test.sh | tee test.log.

Terminate and Resume Process

Pause a running process with Ctrl+Z and resume it with fg (foreground) or bg (background).

Measure Program Runtime

Use the time command to measure execution time, e.g., time ./fibo 30, which reports real, user, and sys times.

Top Memory Processes

List the ten processes consuming the most memory with ps -aux | sort -k4nr | head -n 10.

Search Commands

Find commands related to a task with man -k "copy files", which lists matching manual entries.

Copy‑Paste in Terminal

Use Ctrl+Insert to copy and Shift+Insert to paste in many terminal emulators.

Search Files for a String

Locate files containing a specific string with grep -rn "test", which prints the filename and line number.

Screen Freeze

Pause terminal output with Ctrl+S and resume with Ctrl+Q.

Edit Text Without an Editor

When no editor is available, create a file using cat >file.txt, type the content, then press Ctrl+D to save.

View ELF File

Inspect an ELF binary’s header with readelf -h filename to see architecture, type, and endianness.

Search Symbols in a Library

Check if a library contains a specific symbol using nm filename | grep interface.

Command Editing

Move to the start or end of a command line with Ctrl+A or Ctrl+E. Replace a word in the previous command using ^old^new^.

Alias for Remote Login

Create a shortcut for SSH login, e.g., alias butterfly='ssh -v -l jdoe 192.168.0.11'. Add such aliases to ~/.bashrc for persistence.

Freeze/Unfreeze Terminal

Use Ctrl+S to freeze output and Ctrl+Q to unfreeze.

Reuse Commands

Recall previous commands with !!, !ec (last command starting with “ec”), or !76 (command number 76).

View Log Dynamically

Continuously monitor a log file with tail -f /var/log/syslog.

Help

Most commands provide usage information via the --help option, complementing the manual pages accessed with man.