Pipes are a fundamental concept in Unix-like operating systems, including macOS. They allow the output of one command to be used as the input for another, enabling the chaining of commands to perform complex tasks efficiently. This article will explore the use of pipes in macOS Terminal, providing practical examples and explaining their importance for users who want to streamline their command-line workflows.

Examples:

1. Basic Pipe Usage:

   To demonstrate a simple use of pipes, let's combine the ls and grep commands. The ls command lists files and directories, while grep searches for a specific string within the output.

   ls -l | grep ".txt"

   In this example, ls -l lists all files and directories in the current directory with detailed information. The pipe (|) takes this output and passes it to grep ".txt", which filters the list to show only files with the .txt extension.

2. Combining Multiple Commands:

   Pipes can be used to chain multiple commands together. Here’s an example that uses ps, grep, and wc to count the number of running processes that contain the string "bash".

   ps aux | grep "bash" | wc -l

   • ps aux lists all running processes.
   • grep "bash" filters the list to include only lines containing "bash".
   • wc -l counts the number of lines in the filtered list, giving the number of "bash" processes running.

3. Advanced Usage with sort and uniq:

   Suppose you want to find out how many times each unique word appears in a text file. You can use cat, tr, sort, and uniq together with pipes.

   cat filename.txt | tr -cs "[:alnum:]" "\n" | sort | uniq -c | sort -nr

   • cat filename.txt outputs the contents of the file.
   • tr -cs "[:alnum:]" "\n" translates all non-alphanumeric characters to newlines, effectively splitting words onto new lines.
   • sort sorts the words alphabetically.
   • uniq -c counts the occurrences of each unique word.
   • sort -nr sorts the counts numerically in descending order.