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https://askubuntu.com/q/861522
Title:
In what order does the shell execute commands and stream redirection?
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/2016/12/17/In-what-order-does-the-shell-execute-commands-and-stream-redirection_
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December 17, 2016
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March 13, 2025
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It’s always left to right… except when
Just like in Math we do left to right except multiplication and division is done before addition and subtraction, except operations inside parenthesis (+ -) would be done before multiplication and division.
As per the Bash beginners guide here (Bash Beginners Guide) there are 8 orders of hierarchy of what comes first (before left to right):
- Brace expansion “{}”
- Tilde expansion “~”
- Shell parameter and variable expression “$”
- Command substitution “$(command)”
- Arithmetic expression “$((EXPRESSION))”
- Process Substitution what we are talking about here “<(LIST)” or “>(LIST)”
- Word Splitting “’< space>< tab>< newline>’”
- File Name Expansion “*”, “?”, etc.
So it’s always left to right… except when…