Bash: Process Substitution

Bash: Process Substitution

Process Substitution allows commands to communicate with each other by passing the output of one command as the input to another command, without using temporary files. It uses <() to pass output as input and >() to pass output to another command.


  • Sort the output of a command:

sort <(ls)

This will sort the output of the ls command. <(ls) passes the output of ls as input to sort.

  • Use the output of a command as input to another:

grep pattern <(ls)

This will grep for pattern in the output of ls.

  • Pass output of a command to another command's input:

diff <(command1) <(command2)

This will diff the output of command1 and command2.

  • Send command's output to a file:

command >(file)

This will send the output of command to file instead of stdout.

So in summary, process substitution:

  • Allows commands to communicate without temporary files

  • Uses <() to pass output as input

  • Uses >() to pass output to another command

  • Enables powerful one-liners and data pipelines.

Hope this explanation helps! Let me know if you have any other questions.

Best Practices

  • Use process substitution when you want to pass the output of one command as input to another, without using temporary files.

  • Keep the commands simple. Long or complex commands can make the one-liner hard to read.

  • Use descriptive command names to make the one-liner self-documenting.


Compare two directory listings:

diff <(ls -l directory1) <(ls -l directory2)

Search for a pattern in 'grep' output:

grep pattern <(grep -E "pattern" *)

Pipe 'find' output to 'sort':

<(find . -type f) | sort

In summary, process substitution allows you to pass the output of one command as input to another in a concise, temporary fashion - without using intermediate files. It can help compare, sort, search, and piping command outputs. Keeping the commands simple and self-documenting makes the one-liners easiest to understand and maintain.

Hope these use cases and best practices for process substitution help! Let me know if you have any other questions.

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