log(n) 1.0.2 log "Logging facility"
log - Procedures to log messages of libraries and applications.
package require Tcl 8
package require log ?1.0.2?
The log package provides commands that allow libraries and
applications to selectively log information about their internal
operation and state.
To use the package just execute
| |
package require log
log::log notice "Some message"
|
As can be seen above, each message given to the log facility is
associated with a level determining the importance of the
message. The user can then select which levels to log, what commands
to use for the logging of each level and the channel to write the
message to. In the following example the logging of all message with
level debug is deactivated.
| |
package require log
log::lvSuppress debug
log::log debug "Unseen message" ; # No output
|
By default all messages associated with an error-level
(emergency, alert, critical, and
error) are written to stderr. Messages with any
other level are written to stdout. In the following example
the log module is reconfigured to write debug messages to
stderr too.
| |
package require log
log::lvChannel debug stderr
log::log debug "Written to stderr"
|
Each message level is also associated with a command to use when
logging a message with that level. The behaviour above for example
relies on the fact that all message levels use by default the standard
command ::log::Puts to log any message. In the following example
all messages of level notice are given to the non-standard
command toText for logging. This disables the channel setting
for such messages, assuming that toText does not use it by
itself.
| |
package require log
log::lvCmd notice toText
log::log notice "Handled by \"toText\""
|
Another database maintained by this facility is a map from message
levels to colors. The information in this database has no
influence on the behaviour of the module. It is merely provided as a
convenience and in anticipation of the usage of this facility in
tk-based application which may want to colorize message
logs.
The following commands are available:
- ::log::levels
-
Returns the names of all known levels, in alphabetical order.
- ::log::lv2longform level
-
Converts any unique abbreviation of a level name to the full level
name.
- ::log::lv2color level
-
Converts any level name including unique abbreviations to the
corresponding color.
- ::log::lv2priority level
-
Converts any level name including unique abbreviations to the
corresponding priority.
- ::log::lv2cmd level
-
Converts any level name including unique abbreviations to the command
prefix used to write messages with that level.
- ::log::lv2channel level
-
Converts any level name including unique abbreviations to the channel
used by ::log::Puts to write messages with that level.
- ::log::lvCompare level1 level2
-
Compares two levels (including unique abbreviations) with respect to
their priority. This command can be used by the -command option of
lsort. The result is one of -1, 0 or 1 or an error. A result of -1
signals that level1 is of less priority than level2. 0 signals that
both levels have the same priority. 1 signals that level1 has higher
priority than level2.
- ::log::lvSuppress level {suppress 1}
-
]
(Un)suppresses the output of messages having the specified
level. Unique abbreviations for the level are allowed here too.
- ::log::lvSuppressLE level {suppress 1}
-
]
(Un)suppresses the output of messages having the specified level or
one of lesser priority. Unique abbreviations for the level are allowed
here too.
- ::log::lvIsSuppressed level
-
Asks the package whether the specified level is currently
suppressed. Unique abbreviations of level names are allowed.
- ::log::lvCmd level cmd
-
Defines for the specified level with which command to write the
messages having this level. Unique abbreviations of level names are
allowed. The command is actually a command prefix and this facility
will append 2 arguments before calling it, the level of the message
and the message itself, in this order.
- ::log::lvCmdForall cmd
-
Defines for all known levels with which command to write the messages
having this level. The command is actually a command prefix and this
facility will append 2 arguments before calling it, the level of the
message and the message itself, in this order.
- ::log::lvChannel level chan
-
Defines for the specified level into which channel ::log::Puts
(the standard command) shall write the messages having this
level. Unique abbreviations of level names are allowed. The command is
actually a command prefix and this facility will append 2 arguments
before calling it, the level of the message and the message itself, in
this order.
- ::log::lvChannelForall chan
-
Defines for all known levels with which which channel
::log::Puts (the standard command) shall write the messages
having this level. The command is actually a command prefix and this
facility will append 2 arguments before calling it, the level of the
message and the message itself, in this order.
- ::log::lvColor level color
-
Defines for the specified level the color to return for it in a call
to ::log::lv2color. Unique abbreviations of level names are
allowed.
- ::log::lvColorForall color
-
Defines for all known levels the color to return for it in a call to
::log::lv2color. Unique abbreviations of level names are
allowed.
- ::log::log level text
-
Log a message according to the specifications for commands, channels
and suppression. In other words: The command will do nothing if the
specified level is suppressed. If it is not suppressed the actual
logging is delegated to the specified command. If there is no command
specified for the level the message won't be logged. The standard
command ::log::Puts will write the message to the channel
specified for the given level. If no channel is specified for the
level the message won't be logged. Unique abbreviations of level names
are allowed. Errors in the actual logging command are not
caught, but propagated to the caller, as they may indicate
misconfigurations of the log facility or errors in the callers code
itself.
- ::log::logMsg text
-
Convenience wrapper around ::log::log.
Equivalent to ::log::log info text.
- ::log::logError text
-
Convenience wrapper around ::log::log.
Equivalent to ::log::log error text.
- ::log::Puts level text
-
The standard log command, it writes messages and their levels to
user-specified channels. Assumes that the suppression checks were done
by the caller. Expects full level names, abbreviations are
not allowed.
The package currently defines the following log levels, the level of
highest importance listed first.
-
emergency
-
alert
-
critical
-
error
-
warning
-
notice
-
info
-
debug
log, log level, message, message level
Copyright © 2001-2002 Andreas Kupries <andreas_kupries@users.sourceforge.net>