Question

I need to take a parameter in my Makefile that consists of a host identifier in the form

host[:port]

where the colon and port are optional. So all of the following are valid:

foo.example.com
ssl.example.com:443
localhost:5000

etc.

I want to split the string on the optional colon and assign the values to variables, so that HOST contains foo.example.com, ssl.example.com, localhost, etc., and PORT contains 80 (the default port), 443, and 500 respectively.

Answer 1

# Retrieves a host part of the given string (without port).
# Param:
#   1. String to parse in form 'host[:port]'.
host = $(firstword $(subst :, ,$1))

# Returns a port (if any).
# If there is no port part in the string, returns the second argument
# (if specified).
# Param:
#   1. String to parse in form 'host[:port]'.
#   2. (optional) Fallback value.
port = $(or $(word 2,$(subst :, ,$1)),$(value 2))

Usage:

$(call host,foo.example.com) # foo.example.com
$(call port,foo.example.com,80) # 80

$(call host,ssl.example.com:443) # ssl.example.com
$(call port,ssl.example.com:443,80) # 443