apropos does a keyword search. In the past the keyword was a regular expression On FreeBSD 10 you can run: # search for 'f.*bar' $ apropos 'f.*bar' | wc -l 4 # or dump the database apropos '.' | wc -l 5582 On FreeBSD12-current $ apropos 'f.*bar' | wc -l apropos: nothing appropriate 0 $ apropos '.' | wc -l 318 To use regular expression, you need to prefix the tilde now: $ apropos '~f.*bar' | wc -l 2 apropos '~.' | wc -l 4488 I do not like this change. We are incompatible with anything before in FreeBSD, and we are incompatible with the gnu tools on debian/ubuntu/centos.
This may be no longer true. I get the same number of results for both '.' and '~.' (9072).
(In reply to Piotr Pawel Stefaniak from comment #1) I get the same number of results for both '.' and '~.' too now. $ apropos '.'|wc -l 9517 $ apropos '~.'|wc -l 9517 However, the result number on FreeBSD 14.0-CURRENT are still weird. # case sensitive regex $ apropos '~f.*bar' | wc -l 4 # case insensitive regex $ apropos 'f.*bar' | wc -l 5 # regex by grep $ apropos . | grep 'f.*bar' | wc -l 7 $ apropos . | grep -i 'f.*bar' | wc -l 8 On centos8 it looks better: $ apropos 'f.*bar' | wc -l 10 $ apropos . | egrep -i 'f.*bar' |wc -l 10