The Pipe Command ( | )

One of the most underutilized features in Linux is the pipe command, represented by the | symbol. This seemingly simple character is, in fact, one of the most versatile tools available.

In essence, the pipe allows you to execute two commands simultaneously, using the output from the first command as input for the second. For example:

cat readme.txt | grep “Read me”

This command retrieves the content of the file "readme.txt" and then filters it for any occurrences of the phrase "Read me." While it’s possible to achieve this without the pipe, incorporating it enhances readability and simplifies task management for developers.

Another practical example is:

ps -ef | grep -i <string>

This command is especially beneficial for those managing servers or processes. It enables you to search through running processes for a specific string, which can be vital if, for example, you’ve accidentally paused a Node.js server with "Ctrl+Z." By running:

ps -ef | grep -i node

you can easily locate the lingering process, obtain its process ID, and terminate it if necessary. Using “-ef” with ps provides detailed information about the processes, while “-i” with grep allows for case-insensitive searching—useful unless you know the exact string you’re looking for.

Learn about essential terminal commands every developer should know.

Section 1.1: The Cat Command

The "cat" command is another fundamental tool in Linux. It enables users to display the contents of a file directly in the terminal, making it perfect for quick checks without the need for extensive file management.

In my previous quality assurance role, I often found myself needing to examine log files to diagnose issues. Using the cat command was significantly faster than navigating through file directories with a graphical interface, especially when the relevant information was typically located at the end of the file.

If the file is too large for comfortable reading, you can still extract necessary information with grep:

cat filename.txt | grep -i "relevant information"

This command retrieves only the lines containing the searched string. However, be aware that if relevant details are located on adjacent lines, they might not appear in the output.

Photo by Timothy Meinberg on Unsplash

Section 1.2: Mastering Vi Commands

Navigating the vi text editor can be challenging initially, but mastering a few commands can greatly enhance your efficiency:

• vi <filename>: Opens a file in the vi editor
• :q: Exits the vi editor
• :q!: Exits without saving changes
• :w: Saves changes to the file
• :wq: Saves and exits
• /<string>: Searches for a string in the file; use “n” for the next match and “Shift+n” for the previous one

These are just a few shortcuts to help you get started with vi. While there are many more commands, these basics will assist you in making essential edits.