Puppet

Motivation for having this function:

The general problem is that I get some value, for example from a fact or from a parameter to a definition, that needs to be formatted in some way for the specific use it is being put to. regsubst() can also be used for extracting parts of such values.

As a concrete problem I will be solving, I have a large number of machines that are connected with Ethernet and Infiniband. They should have IP addresses on both networks, for example the machine named n23 should have 10.17.0.23 on the Ethernet net, and 10.18.0.23 on the Infiniband net. On the ethernet network, they get their IP addresses using DHCP (and the dhcpd.conf file is generated with an ERB template). However, none of the DHCP clients I have seen, and few of the DHCP servers, can handle Infiniband. Thus, I want Puppet to derive the node’s Infiniband IP address from its Ethernet IP address. With regsubst() and sprintf() I can do that like this:

 $ipre = '^([0-9]+)[.]([0-9]+)[.]([0-9]+)[.]([0-9]+)$'
 $i1 = regsubst($ipaddress_eth0, $ipre, '\1')
 $i2 = regsubst($ipaddress_eth0, $ipre, '\2')
 $i3 = regsubst($ipaddress_eth0, $ipre, '\3')
 $i4 = regsubst($ipaddress_eth0, $ipre, '\4')
 $ibip = sprintf("%d.%d.%d.%d", $i1, $i2 + 1, $i3, $i4)

(This uses the sprintf() function requested in #1831.)