confmodule man page
confmodule — communicate with Debian configuration system FrontEnd.
db_input 'foo/bar' || true
db_go || true
This is a library of shell functions that eases communication with Debian's configuration management system. It can communicate with a FrontEnd via the debconf protocol. The design is that each command in the protocol is represented by one function in this module. The functionname is the same as the command, except it is prefixed with "db_" and is lower-case. Call the function and pass in any parameters you want to follow the command. Any textual return code from the FrontEnd will be returned to you in the $RET variable, while the numeric return code from the FrontEnd will be returned as a return code (and so those return codes must be captured or ignored).
Once this library is loaded, any text you later output will go to standard error, rather than standard output. This is a good thing in general, because text sent to standard output is interpreted by the FrontEnd as commands. If you do want to send a command directly to the FrontEnd, you must output it to file descriptor 3, like this:
echo GET foo/bar >&3
The library checks to make sure it is actually speaking to a FrontEnd by examining the DEBIAN_HAS_FRONTEND variable. If it is set, a FrontEnd is assumed to be running. If not, the library turns into one, and runs a copy of the script that loaded the library connected to it. This means that if you source this library, you should do so very near to the top of your script, because everything before the sourcing of the library may well be run again.
debconf-devel(7), dpkg-preconfigure(8), dpkg-reconfigure(8), debconf_specification in the debian-policy package
Joey Hess <firstname.lastname@example.org>