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Added some guidelines and recommendations to the 'Logging' section of PLUGINS.html

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Klaus Schmidinger 2017-04-02 13:01:34 +02:00
parent c4cc5e613c
commit fe535d25e5
2 changed files with 28 additions and 0 deletions
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@ -8944,3 +8944,7 @@ Video Disk Recorder Revision History
store auxiliary information with an event (thanks to Jörg Wendel). This string
has no meaning whatsoever to VDR itself, and it will not be written into the
info file of a recording that is made for such an event.
- Added some guidelines and recommendations to the 'Logging' section of PLUGINS.html.
The most important being: implement a command line option to control the level
of logging (in particular allow turning off logging completely!) and never print
anything to stdout or stderr (unless one of the listed exceptions applies).

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PLUGINS.html
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@ -583,6 +583,30 @@ esyslog("pluginname: error #%d has occurred", ErrorNumber);
Note that the log messages will be given as provided, the plugin's name will not
automatically be added, so make sure your log messages are obvious enough.
<p>
<modified>
Only use the above logging functions for occasional log messages. Do not use
them unconditionally for frequent messages that produce long sequences of lines
in the log file every few seconds. That might make it hard to work on other plugins
or the core VDR code, watching their log entries while they are permanently
interspersed with unrelated stuff.<br>
<br>
The recommended behavior for a plugin that does logging is to implement a command
line option that controls the level of log messages, preferably '-l N, --log=N',
where 'N' is in the range 0...3, with 0 meaning no logging whatsoever, 1 log only
errors, 2 log errors and informational messages, and 3 also log debug information.<br>
<br>
If a plugin can output extensive data for special debugging purposes (either to
the log file or stdout/stderr), this should be enabled by setting proper switches
in one of its source files (see for example how the communication between VDR and
CAMs can be monitored in VDR/ci.c).<br>
<br>
Under no circumstances must a plugin print anything to stdout or stderr during
normal operation! The only exceptions being special debug information as described
above, fatal error messages that will cause VDR to abort, or if it is the sole
purpose of the plugin to display something on stdout, like for instance the
<i>skincurses</i> plugin, which displays the OSD at the console.
</modified>
<hr><h2><a name="Main menu entry">Main menu entry</a></h2>