How to use process substitution in bash

Short answer

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

Steps

1. Compare command outputs:

diff <(sort file1.txt) <(sort file2.txt)

2. Pass command output as a file argument:

wc -l <(find /var/log -name "*.log")

3. Write to a process:

echo "data" >(cat > output.txt)

Tips

• Process substitution creates named pipes behind the scenes.
• More convenient than creating temporary files manually.
• Works in bash and zsh; not in plain POSIX sh.

Common issues

• Some commands require seekable files and do not work with pipes.
• Nested process substitution can be hard to read; use sparingly.