Pipe

When you work in Windows, macOS, and most other operating systems, you probably spend your time running applications like web browsers, word processors, spreadsheets, and games. A typical application is packed with features: everything that the designers thought their users would need. So, most applications are self-sufficient.

The Linux command line is different. Instead of big applications with tons of features, Linux supplies thousands of small commands with very few features. The command cat, for example, prints files on the screen and that’s about it. ls lists the files in a directory, mv renames files, and so on. Each command has a simple, fairly well-defined purpose. Linux makes it easy to combine commands so their individual features work together to accomplish your goal. This way of working yields a very different mindset about computing. Instead of asking Which app should I launch? to achieve some result, the question becomes Which commands should I combine?.

The | operator lets you to connect the output of one command to the input of another command. This allows for powerful command chaining and the ability to perform complex operations using simple commands. The syntax for using the pipe is as follows:

• Example usage:

    command1 | command2 # Pipes the output of 'command1' as input to 'command2'

    ls -l | sort -k 5rn # Lists files in long format and pipes the output to sort files by the fifth column in reverse numerical order

    cat file1.txt file2.txt | sort > sorted_combined.txt # Concatenates content from 'file1.txt' and 'file2.txt', then sorts the combined content and saves it to 'sorted_combined.txt'

    cat file.txt | sort | uniq # Sorting and getting unique lines in a file

    ls -l | awk '{print $5}' # Prints the file sizes from ls -l command

    ps -aux | grep "firefox" # Lists details of running processes related to Firefox

    cat app.log | grep "ERROR" # Displays lines containing 'ERROR' in app.log

    du -ah | sort -rh | head -n 5 # Lists the top 5 largest files in a directory

    cat romeo_and_juliet.txt | grep -i "romeo" | wc -l # Counts the occurrences of "Romeo" (case-insensitive) in the text file

    shuf data.txt | head -n 10 > newfile.txt # Shuffles the lines in 'data.txt', selects the first 10 lines, and saves them in 'newfile.txt'