Logstash - make input file path configurable

Elastic Stack Logstash
3

Lets assume my logstash configuration to be

input {
file {
path => "/var/tmp/*"
}
}

i want the ability to pass /var/tmp/* in some manner say like replacement of a variable

input {
file {
path => "$TO_REPLACE"
}
}

and pass TO_REPLACE during start up like logstash -f config.conf -DTO_REPLACE="/var/tmp/*"

Thanks,
sam