Essential Linux Command-Line Tricks Every Engineer Should Know

As a daily Linux engineer, I rely heavily on the command line and often forget useful tricks unless I practice them, so I gathered a set of handy tips to avoid future forgetfulness.

Display command output as a clear table

Typical command output can be a tangled mess, e.g., the mount command. Adding column -t formats it into a readable table. mount | column -t You can also change the delimiter, for example using a colon:

cat /etc/passwd | column -t -s:

Repeat a command until it succeeds

Many users search for ways to keep retrying a command until it works. A simple while true loop can achieve this.

The redirection >/dev/null 2>&1 discards both standard output and error.

Sort processes by memory usage

ps aux | sort -rnk 4

Sort processes by CPU usage

ps aux | sort -nk 3

To check your machine architecture, run getconf LONG_BIT.

View multiple log files simultaneously

The multitail command can monitor several logs with highlighting and filtering.

Install it with apt-get install multitail.

Return to the previous directory

Simply use cd - to go back.

Make a non‑interactive shell session interactive

Switch your startup file from ~/.bashrc to ~/.bash_profile.

Periodic monitoring of command output

Use watch (e.g., watch df -h) to repeatedly display any command’s output.

Keep a program running after the session ends

Run commands with nohup to prevent them from being terminated when the shell closes.

nohup wget site.com/file.zip

The output is saved to nohup.out.

Automatically answer Yes or No

Use yes to feed affirmative responses: yes | apt-get update. To answer “No”, pipe yes no into the command.

Create a file of a specific size

Use dd to generate a file of a given size, e.g., a 10 MB zero‑filled file:

dd if=/dev/zero of=out.txt bs=1M count=10

Run the last command as root

If you forget to prepend sudo, simply type sudo !! to re‑execute the previous command with root privileges.

Record a shell session

Use script to capture everything typed in the terminal into a file (e.g., typescriptscript), which is finalized when you exit.

Replace spaces with another delimiter

The tr command can substitute any character. Example:

cat geeks.txt | tr ':' '\t' > out.txt

Convert file content to upper or lower case

Example to convert to uppercase:

cat myfile | tr a-z A-Z > output.txt

Powerful xargs command

xargs

feeds the output of one command as arguments to another. Examples:

find . -name "*.png" -type f -print | xargs tar -cvzf images.tar.gz

cat urls.txt | xargs wget

Use -i with a placeholder to insert each item into a command:

ls /etc/*.conf | xargs -i cp {} /home/likegeeks/Desktop/out

These are just a few of the many Linux command‑line tricks; tools like awk and sed can further extend your capabilities.