Bash · Jan 20, 2023 · 1 min read
Process substitution is a feature in bash that allows the output of a command or process to be used as input to another command or process, eliminating the need to write the output to a temporary file first. This is achieved by utilizing the special syntax <() on the command line.
For example, consider the following command:
$ gpg --encrypt --hidden-recipient-file <(curl -sL https://example.com/hidden-recipient.gpg) --output message.gpg message.txt
This command utilizes the gpg command to encrypt the file message.txt, using the recipient's public key that is downloaded via curl from the specified URL, and uses bash process substitution with <() to pass the contents of the downloaded file to the --hidden-recipient-file option of gpg.
In summary, process substitution is an efficient way to use the output of a command as input to another command, without the need to write the output to a temporary file first.
Cooper, M. (2006). Advanced Bash-Scripting Guide. Advanced Bash-Scripting Guide. https://linux.die.net/abs-guide/process-sub.html