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ActiveTcl User Guide
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logger(n) 0.1.0 "Object Oriented logging facility"
logger - System to control logging of events.
package require Tcl 8
package require logger ?0.1.0?
The logger package provides a flexible system
for logging messages from different services, at priority levels,
with different commands.
To begin using the logger package, we do the following:
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package require logger
set log [logger::init myservice]
${log}::notice "Initialized myservice logging"
... code ...
${log}::notice "Ending myservice logging"
${log}::delete
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In the above code, after the package is loaded, the following
things happen:
- logger::init service
- Initializes the service service for logging.
The service names are actually Tcl namespace names, so they are
seperated with '::'. When a logger service is initalized, it
"inherits" properties from its parents. For instance, if there were
a service foo, and we did a logger::init foo::bar (to create a
bar service underneath foo), bar would
copy the current configuration of the foo service,
although it would of course, also be possible to then seperately
configure bar.
- logger::services
- Returns a list of all the available services.
- logger::enable level
- Globally enables logging at or "above" the given level. Levels
are debug, info,
notice, warn,
error, critical.
- logger::disable level
- Globally disables logging at or "below" the given level. Levels
are those listed above.
- ${log}::debug message
- ${log}::info message
- ${log}::notice message
- ${log}::warn message
- ${log}::error message
- ${log}::critical message
- These are the commands called to actually log a message about
an event. ${log} is the variable obtained from logger::init.
- ${log}::setlevel level
- Enable logging, in the service referenced by
${log}, and its children, at or above the level
specified, and disable logging below it.
- ${log}::enable level
- Enable logging, in the service referenced by
${log}, and its children, at or above the level
specified. Note that this does not disable logging below
this level, so you should probably use setlevel
instead.
- ${log}::disable level
- Disable logging, in the service referenced by
${log}, and its children, at or below the level
specified. Note that this does not enable logging above
this level, so you should probably use setlevel
instead.
- ${log}::logproc level argname body
- This is a command to define a command that will perform the
actual logging for a given level. The logger package ships with
default commands for all log levels, but with logproc it is possible to replace them with custom code.
This would let you send your logs over the network, to a database,
or anything else. For example:
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${log}::logproc notice txt {
puts $netlog "Notice: $txt"
}
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- ${log}::services
- Returns a list of all the registered logging services.
- ${log}::delete
- This command deletes a particular logging service, and its
children. You must call this to clean up the resources used by a
service.
The logger package is implemented in such a way as to optimize
(for Tcl 8.4 and newer) log procedures which are disabled. They are
aliased to a proc which has no body, which is compiled to a no op
in bytecode. This should make the peformance hit minimal. If you
really want to pull out all the stops, you can replace the ${log}
token in your code with the actual namespace and command
(${log}::warn becomes ::logger::tree::myservice::warn), so that no
variable lookup is done. This puts the performance of disabled
logger commands very close to no logging at all.
The "object orientation" is done through a hierarchy of
namespaces. Using an actual object oriented system would probably
be a better way of doing things, or at least provide for a cleaner
implementation.
The service "object orientation" is done with namespaces.
log , log level , logger , service