bash what means quotes inside asterisk *"str"*

I have an example

o="o"
if [[ *"aoei"* == $o ]]; then echo 5; fi;

What means asterisk in this example?

p.s. is order important? if [[ *"o"* == $o ]] vs if [[ $o == *"o"* ]]

1 Answer

Order is crucial. As documented for the [[ conditional construct, the == operator is a pattern matching operator where the right-hand side is a glob pattern (aka "wildcard").

• [[ *"o"* == $o ]] tests if the literal string *o* matches the pattern contained in the variable $o
• [[ $o == *"o"* ]] tests if the string contained in the variable $o matches the pattern *o* (i.e. if the contents of $o contains an o)

Note that the pattern *"aoei"* means: zero or more of any character, followed by the exact sequence aoei, followed by zero or more of any character. Perhaps you intended the pattern *[aoei]* which means: contains an a or an o or an e or an i.

Demonstrating:

$ o="o"
$ if [[ *"aoei"* == $o ]]; then echo 5; fi; # no output
$ if [[ $o == *"aoei"* ]]; then echo 5; fi; # no output
$ o="AaoeiBC"
$ if [[ *"aoei"* == $o ]]; then echo 5; fi; # no output
$ if [[ $o == *"aoei"* ]]; then echo 5; fi;
5
$ o="o"
$ if [[ *[aoei]* == $o ]]; then echo 5; fi; # no output
$ if [[ $o == *[aoei]* ]]; then echo 5; fi;
5