Provided by: tcllib_1.14-dfsg-1_all bug

NAME

       log - Procedures to log messages of libraries and applications.

SYNOPSIS

       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

_________________________________________________________________

DESCRIPTION

       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.

API

       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.

LEVELS

       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.

BUGS, IDEAS, FEEDBACK

       This document, and the package it describes,  will  undoubtedly  contain  bugs  and  other
       problems.    Please   report   such  in  the  category  log  of  the  Tcllib  SF  Trackers
       [http://sourceforge.net/tracker/?group_id=12883].   Please  also  report  any  ideas   for
       enhancements you may have for either package and/or documentation.

KEYWORDS

       log, log level, message, message level

CATEGORY

       Programming tools

COPYRIGHT

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