In a script /etc/network/if-up.d/avahi-autoipd in my system, I find statements like this:
case "$ADDRFAM" in
inet|NetworkManager) ;;
*) exit 0
esac
case "$METHOD" in
static|dhcp|NetworkManager) ;;
*) exit 0
esac
The pipe character | seems like the logic "or", but I can't find this rule in the guide. I can only find | used as the command pipe and the "bitwise or" for the arithmetic integer.
Can anyone tell me what's the usage in this case?
In the pattern clauses of a case statement, | means precisely or.
From the bash manual on case:
The syntax of the case command is:
case word in [ [(] pattern [| pattern]…) command-list ;;]… esac
The ‘|’ is used to separate multiple patterns, and the ‘)’ operator terminates a pattern list.
or only in the patterns, right?
$((...)) or, in bash and some other shells, the command ((...))), | is the "bitwise-or" operator. (Eg. echo $((18|3)) outputs 19). In bash, if the extglob shell option is enabled (as by default), then | may be used in an "extended glob" pattern to indicate alternation ("or"). See gnu.org/software/bash/manual/bashref.html#Pattern-Matching