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Razor confupdate

SokoloffA edited this page Sep 4, 2012 · 1 revision

README razor-confupdate

Version: 0.5

Copyright: 2012 Razor team

Author: Alexander Sokoloff sokoloff.a@gmail.com

Program based on kconf_update utility. Copyright (c) 2001 Waldo Bastian bastian@kde.org, bastian@suse.com

What it does

razor-confupdate is a tool designed to update config files. Over time applications sometimes need to rearrange the way configuration options are stored. Since such an update shouldn't influence the configuration options that the user has selected, the application must take care that the options stored in the old way will still be honored.

What used to happen is that the application looks up both the old and the new configuration option and then decides which one to use. This method has several drawbacks:

  • The application may need to read more configuration files than strictly needed, resulting in a slower startup.
  • The application becomes bigger with code that will only be used once.

razor-confupdate addresses these problems by offering a framework to update configuration files without adding code to the application itself.

How it works

Applications can install so called "update files" under $XDG_DATA_HOME/razor/razor-confupdate and $XDG_DATA_DIRS/razor/razor-confupdate 1. An update file has ".upd" as extension and contains instructions for transferring/converting configuration information from one place to another.

Updating the configuration happens automatically, either when Razor-qt gets started or when razor-session detects a new update file in the above mentioned location.

Update files are separated into sections. Each section has an Id. When a section describing a configuration change has been applied, the Id will be stored in the file "razor-confupdate.conf". This information is used to make sure that a configuration update is only performed once.

If you overwrite an existing update file with a new version that contains a new section, only the update instructions from this extra section will be performed.

File format of the update file

Empty lines or lines that start with '#' are considered comments. Commas (,) are used to seperate fields and may not occur as part of any field and all of the keywords are case-sensitive, i.e. you cannot say "key" instead of "Key" for example.

For the rest the file is parsed and executed sequentially from top to bottom. Each line can contain one entry. The following entries are recognized:

Id=<id>

With <id> identifying the group of update entries that follows. Once a group of entries have been applied, their <id> is stored and this group of entries will not be applied again.

File=<oldfile>,<newfile> File=<oldfile>

A path can either be relative or absolute, or starts from "~" (tilde). A relative path defines a location that is relative to the $XDG_CONFIG_HOME directory. If $XDG_CONFIG_HOME is either not set or empty, a default equal to $HOME/.config should be used.

Specifies that configuration information is read from <oldfile> and written to <newfile>. If you only specify <oldfile>, the information is read from as well as written to <oldfile>. Note that if the file does not exist at the time razor-confupdate first checks, no related update will be performed (script won't be run at all, etc.).

Script=<script>[,<interpreter>]

All entries from <oldfile> are piped into <script>. The output of script is used as new entries for <newfile>. Existing entries can be deleted by adding lines with "# DELETE [group]key" in the output of the script. To delete a whole group use "# DELETEGROUP [group]".

<script> should be installed into same dir where .upd file is located, or razor-confupdate will not be able to find it. It's also possible to install applications in /usr/<local>/lib<libsuffix>/razor-confupdate_bin, which opens the door to razor-confupdate applications that are written in C++ and use Qt's powerful string API instead.

If Script was issued after a "Group" command the behavior is slightly different: All entries from <oldfile>/<oldgroup> are piped into <script>. The output of script is used as new entries for <newfile>/<newgroup>, unless a different group is specified with "[group]". Existing entries can be deleted from <oldgroup> by adding lines with "# DELETE key" in the output of the script. To delete <oldgroup> use "# DELETEGROUP".

<interpreter> can be something like "perl".

It is also possible to have a Script without specifying <oldfile> or <newfile>. In that case the script is run but it will not be fed any input and its output will simply be discarded.

ScriptArguments=<arguments>

If specified, the arguments will be passed to <script>. IMPORTANT: It has to be specified before Script=.

Group=<oldgroup>,<newgroup> Group=<oldgroup>

Specifies that configuration information is read from the group <oldgroup> and written to <newgroup>. If you only specify <oldgroup>, the information is read from as well as written to <oldgroup>. You can use <default> to specify keys that are not under any group. A group may be written either as "group" or as "[group]". The latter syntax makes it possible to specify subgroups: "[group][subgroup]".

RemoveGroup=<oldgroup>

Specifies that <oldgroup> is removed entirely. This can be used to remove obsolete entries or to force a revert to default values.

Options=<option1>, <option2>, ....

With this entry you can specify options that apply to the next "Script", "Key" or "AllKeys" entry (only to the first!). Possible options are:

  • "copy" Copy the configuration item instead of moving it. This means that the configuration item will not be deleted from <oldfile>/<oldgroup>.

  • "overwrite" Normally, a configuration item is not moved if an item with the new name already exists. When this option is specified the old configuration item will overwrite any existing item.

Key=<oldkey>,<newkey> Key=<oldkey>

Specifies that configuration information is read from the key <oldkey> and written to <newkey>. If you only specify <oldkey>, the information is read from as well as written to <oldkey>.

AllKeys

Specifies that all configuration information in the selected group should be moved (All keys).

AllGroups

Specifies that all configuration information from all keys in ALL groups should be moved.

RemoveKey=<oldkey>

Specifies that <oldkey> is removed from the selected group. This can be used to remove obsolete entries or to force a revert to default values.

Example update file

# This is comment
Id=Razor0.4.1
File=kioslaverc,kio_httprc
Group=Proxy Settings
Key=NoProxyFor
Key=UseProxy
Key=httpProxy,Proxy
Group=Cache Settings,Cache
Key=MaxCacheSize
Key=UseCache
Group=UserAgent
AllKeys
RemoveGroup=KDE
# End of file

The above update file extracts config information from the file "kioslaverc" and stores it into the file "kio_httprc".

It reads the keys "NoProxyFor", "UseProxy" and "httpProxy" from the group "Proxy Settings" in the "kioslaverc" file. If any of these options are present they are written to the keys "NoProxyFor", "UseProxy" and "Proxy" (!) in the group "Proxy Settings" in the "kio_httprc" file.

It also reads the keys "MaxCacheSize" and "UseCache" from the group "Cache Settings" in the "kioslaverc" file and writes this information to the keys "MaxCacheSize" and "UseCache" in the group "Cache" (!) in the "kio_httprc" file.

Then it takes all keys in the "UserAgent" group of the file "kioslaverc" and moves then to the "UserAgent" group in the "kio_httprc" file.

Finally it removes the entire "KDE" group in the kioslaverc file.

Debugging and testing

If you are developing a razor-confupdate script and want to test or debug it you need to make sure razor-confupdate runs again after each of your changes. There are a number of ways to achieve this.

The easiest is to not install the razor-confupdate script in the first place, but manually call it through a pipe. If you want to test the update script for your application KHello's config file khellorc, you can test by using

cat ~/.config/hello.conf | hello_confupdate.sh

(assuming hello_confupdate.sh is the confupdate script). This is easier than making install every time, but has the obvious downside that you need to 'parse' your script's output yourself instead of letting razor-confupdate do it and check the resulting output file.

After 'make install' the confupdate script is run, but it does so only once. This is of course the idea behind it, but while developing it can be a problem. You can increase the revision number for each subsequent run of 'make install' to force a new razor-confupdate run, but there's a better approach that doesn't skyrocket the version number for a mediocre debug session.

razor-sesion doesn't really ignore scripts that it has already run right away. Instead it checks the affected config file every time a .upd file is added or changed. The reason it still doesn't run again on your config file lies in the traces razor-confupdate leaves behind: it adds a special config group '[Version]' with a key 'update_info'. This key lists all confupdate scripts that have already been run on this config file. It also adds a group for the script to razor-confupdate.conf. Just remove your script entries from both your config file and razor-confupdate.conf, 'make install', and razor-confupdate will happily run your script again, without you having to increase the version number.

If you want to know what razor-confupdate has been up to lately, have a look at ~/.local/share/razor/razor-confupdate.log

Common Problems

  • razor-confupdate refuses to update an entry If you change the value of an entry without changing the key or file, make sure to tell razor-confupdate that it should overwrite the old entry by adding "Options=overwrite".

Notes

[1] - http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

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