Plumber (program)

The plumber, in the Plan 9 from Bell Labs and Inferno operating systems, is a mechanism for reliable uni- or multicast inter-process communication of formatted textual messages. It uses the Plan 9 network file protocol, 9P, rather than a special-purpose IPC mechanism.

Any number of clients may listen on a named port (a file) for messages. Ports and port routing are defined by plumbing rules. These rules are dynamic. Each listening program receives a copy of matching messages. For example, if the data /sys/lib/plumb/basic is plumbed with the standard rules, it is sent to the edit port. The port will write a copy of the message to each listener. In this case, all running editors will interpret this message as a file name, and open the file.

The plumber is the 9P file server that provides this service. Clients may use libplumb to format messages. Since the messages are 9P, they are network transparent.

Example
The following is an example of plumbing rules: addr=':(#?[0−9]+)' protocol='(https?|ftp|file|gopher|mailto|news|nntp|telnet|wais)' domain='[a−zA−Z0−9_@]+([.:][a−zA−Z0−9_@]+)*/?[a−zA−Z0−9_?,%#~&/\−]+' file='([:.][a−zA−Z0−9_?,%#~&/\−]+)*' type is text data matches '[a−zA−Z0−9_\−./]+' data matches '([a−zA−Z0−9_\−./]+).(jpe?g|gif|bit)' arg isfile $0 plumb to image plumb start page −w $file type is text data matches $protocol://$domain$file plumb to web plumb start window webbrowser $0 type is text data matches '([.a−zA−Z0−9_/–]+[a−zA−Z0−9_/\−])('$addr')?' arg isfile $1 data set $file attr add addr=$3 plumb to edit plumb start window sam $file type is text data matches '([a−zA−Z0−9]+\.h)('$addr')?' arg isfile /sys/include/$1 data set $file attr add addr=$3 plumb to edit plumb start window sam $file
 * 1) these are generally in order from most specific to least,
 * 2) since first rule that fires wins.
 * 1) image files go to page
 * 1) URLs go to web browser
 * 1) existing files, possibly tagged by line number, go to edit/sam
 * 1) .h files are looked up in /sys/include and passed to edit/sam