Process substitution (<() and >()) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is process substitution in bash?

Process substitution lets you use the output or input of a command as if it were a file. It uses <() for input and >() for output.

beginner

How does <() work in bash?

The <() syntax runs a command and provides its output as a temporary file name. You can use this file name as input to another command.

intermediate

What does >() do in bash scripting?

The >() syntax runs a command and provides a temporary file name that acts like a writable file. Writing to this file sends data to the command's input.

beginner

Example: How to compare the output of two commands using diff and process substitution?

Use: diff <(command1) <(command2). This compares the outputs of command1 and command2 without creating temporary files manually.

intermediate

Why use process substitution instead of temporary files?

Process substitution is cleaner and faster. It avoids creating and deleting temporary files manually and works well in pipelines.

What does <(command) do in bash?

A Redirects command output to a file

B Runs command and waits for user input

C Runs command and provides its output as a file name

D Creates a new file with command's name

<(command) runs the command and gives a file name that contains the command's output.

Which symbol is used for output process substitution?

A <()

B >>

C |

D >()

>() runs a command and provides a writable file name to send data into the command.

How can you compare outputs of two commands without temporary files?

A diff <(command1) <(command2)

B diff file1 file2

C cat command1 command2

D diff command1 command2

diff <(command1) <(command2) compares outputs directly using process substitution.

Process substitution is useful because it:

A Requires manual file cleanup

B Avoids temporary files and simplifies pipelines

C Creates permanent files

D Slows down scripts

It avoids temporary files and makes pipelines cleaner and faster.

Which of these is NOT true about process substitution?

A It works only on Windows

B It creates named pipes or /dev/fd files

C It can be used with commands expecting file names

D It helps redirect command input or output

Process substitution is a feature of Unix-like shells, not Windows.

Explain how process substitution works in bash and give an example using <() or >().

Think about how commands can be treated like files.

Describe the benefits of using process substitution compared to temporary files in scripting.

Consider what makes scripting easier and cleaner.