Regex quantifiers are not working well with locate

Question

This output is rather self-explanatory:

XXXXX@debianvirtualbox:~$ locate -r "^/var/lib/tomcat[0-9]/.*" -l 10
/var/lib/tomcat8/conf
/var/lib/tomcat8/lib
/var/lib/tomcat8/logs
/var/lib/tomcat8/webapps
/var/lib/tomcat8/work
/var/lib/tomcat8/webapps/ROOT
/var/lib/tomcat8/webapps/websight
/var/lib/tomcat8/webapps/ROOT/META-INF
/var/lib/tomcat8/webapps/ROOT/index.html
/var/lib/tomcat8/webapps/ROOT/META-INF/context.xml
jakub@maredadebianvirtualbox:~$ locate -r "^/var/lib/tomcat[0-9]{1,2}/.*" -l 10
XXXXX@debianvirtualbox:~$

I am trying to list first ten (-l 10) entries matching tomcat installation directory. If I just use [0-9] it properly matches tomcat8, however if I add a quantifier [0-9]{1,2} it matches nothing. Same goes for quantifiers + and ?, however * seems to work fine and so does this expression:

^/var/lib/tomcat[0-9][0-9]*/.*

Why this happens and what's a good workaround?

Answer 1

Try --regex (without a 'p') rather than -r (aka --regexp). This tells locate to use extended regexps rather than basic.

locate --regex "^/var/lib/tomcat[0-9]{1,2}/" -l 10 

alternatively, escape { and } with \ to make them special in basic regex.