DOKK / manpages / debian 10 / tcllib / log.3tcl.en
log(3tcl) Logging facility log(3tcl) 







log - Procedures to log messages of libraries and
  applications.








package require Tcl 8


package require log ?1.3?


::log::levels


::log::lv2longform level


::log::lv2color level


::log::lv2priority level


::log::lv2cmd level


::log::lv2channel level


::log::lvCompare level1 level2


::log::lvSuppress level {suppress 1}


::log::lvSuppressLE level {suppress 1}


::log::lvIsSuppressed level


::log::lvCmd level cmd


::log::lvCmdForall cmd


::log::lvChannel level chan


::log::lvChannelForall chan


::log::lvColor level color


::log::lvColorForall color


::log::log level text


::log::logarray level arrayvar
    ?pattern?


::log::loghex level text data


::log::logMsg text


::log::logError text


::log::Puts level text












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::logarray level arrayvar ?pattern?

  
Like ::log::log, but logs the contents of the specified array
      variable arrayvar, possibly restricted to entries matching the
      pattern. The pattern defaults to * (i.e. all entries) if
      none was specified.

  
::log::loghex level text data

  
Like ::log::log, but assumes that data contains binary data.
      It converts this into a mixed hex/ascii representation before writing them
      to the log.

  
::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
    • 



Note that by default all messages with levels
    warning down to debug are suppressed. This is done
    intentionally, because (we believe that) in most situations debugging output
    is not wanted. Most people wish to have such output only when actually
    debugging an application.








This document, and the package it describes, will undoubtedly
    contain bugs and other problems. Please report such in the category
    log of the Tcllib Trackers
    [http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for
    enhancements you may have for either package and/or documentation.


When proposing code changes, please provide unified diffs,
    i.e the output of diff -u.


Note further that attachments are strongly preferred over
    inlined patches. Attachments can be made by going to the Edit form of
    the ticket immediately after its creation, and then using the left-most
    button in the secondary navigation bar.








log, log level, message, message level








Programming tools








Copyright (c) 2001-2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>








  

    1.3
    tcllib