Piping Commands (|)

Welcome! In Linux, you often need to combine the power of several commands to get a specific result. This is where pipes come in handy.

A pipe allows you to send the output of one command directly as the input to another command. Think of it like a conveyor belt for data!

The pipe symbol is a vertical bar: |. You place it between two commands.

• The command on the left sends its standard output (what it normally prints to the screen).
• The command on the right receives this output as its standard input.

It's a fundamental concept for efficient command-line work!

Let's see a pipe in action. The ls -l /usr/bin command lists many files, often too many for one screen.

By piping its output to less, you can view it page by page. Try running this example:

Pipes are excellent for filtering. The grep command searches for patterns in text. When combined with a pipe, it can filter the output of another command.

This command lists all files in the current directory and then filters to show only those ending with .txt:

The wc (word count) command can count lines, words, or characters. When used with a pipe, it counts from the piped input.

To count how many .txt files are in the current directory, you can chain ls, grep, and wc -l (count lines):

You're not limited to just two commands! You can chain many commands together with multiple pipes, creating powerful sequences.

Each pipe passes the output of the previous command to the next one in the chain:

The sort command arranges lines of text alphabetically or numerically. It's often used after a pipe to organize data.

This example lists files in /etc and sorts them in reverse alphabetical order, showing only the first 5 results:

The uniq command removes duplicate adjacent lines. It's most effective when used after sort, which brings identical lines together.

Let's sort a list of fruits and then find the unique ones:

Remember I/O redirection (>, >>, <) from the previous lesson?

• Pipes (|): Connect the output of one command to the input of another command. This keeps data flowing between programs.
• Redirection (>, <): Connects a command's input/output to a file. This saves data to disk or reads it from disk.

Both are powerful but serve different purposes.

You've learned how to connect commands using pipes. Let's test your understanding!

Great job! You've mastered the basics of piping commands in Linux.

• Pipes (|) connect the output of one command to the input of another.
• They allow you to chain commands for powerful filtering, sorting, and processing tasks.
• Pipes are distinct from I/O redirection, which connects commands to files.

Keep practicing with different commands and see how much you can achieve by combining them!