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history(n)		     Tcl Built-In Commands		    history(n)

______________________________________________________________________________

NAME
       history - Manipulate the history list

SYNOPSIS
       history ?option? ?arg arg ...?
_________________________________________________________________

DESCRIPTION
       The  history  command  performs	one  of	 several operations related to
       recently-executed commands recorded in a history list.  Each  of	 these
       recorded	 commands  is referred to as an ``event''.  When specifying an
       event to the history command, the following forms may be used:

       [1]    A number:	 if positive, it refers to the event with that	number
	      (all events are numbered starting at 1).	If the number is nega‐
	      tive, it selects an event relative  to  the  current  event  (-1
	      refers  to the previous event, -2 to the one before that, and so
	      on).  Event 0 refers to the current event.

       [2]    A string:	 selects  the  most  recent  event  that  matches  the
	      string.	An  event  is considered to match the string either if
	      the string is the same as the first characters of the event,  or
	      if the string matches the event in the sense of the string match
	      command.

       The history command can take any of the following forms:

       history
	      Same as history info, described below.

       history add command ?exec?
	      Adds the command argument to the history list as	a  new	event.
	      If  exec	is specified (or abbreviated) then the command is also
	      executed and its result is returned.  If	exec  isn't  specified
	      then an empty string is returned as result.

       history change newValue ?event?
	      Replaces	the  value recorded for an event with newValue.	 Event
	      specifies the event to replace,  and  defaults  to  the  current
	      event  (not event -1).  This command is intended for use in com‐
	      mands that implement new forms of history substitution and  wish
	      to  replace  the	current event (which invokes the substitution)
	      with the command created through substitution.  The return value
	      is an empty string.

       history clear
	      Erase  the  history  list.   The current keep limit is retained.
	      The history event numbers are reset.

       history event ?event?
	      Returns the value of the event given by event.   Event  defaults
	      to -1.

       history info ?count?
	      Returns  a formatted string (intended for humans to read) giving
	      the event number and contents for each of the events in the his‐
	      tory  list except the current event.  If count is specified then
	      only the most recent count events are returned.

       history keep ?count?
	      This command may be used to change the size of the history  list
	      to  count events.	 Initially, 20 events are retained in the his‐
	      tory list.  If count is not specified, the current keep limit is
	      returned.

       history nextid
	      Returns  the number of the next event to be recorded in the his‐
	      tory list.  It is useful for things like printing the event num‐
	      ber in command-line prompts.

       history redo ?event?
	      Re-executes  the	command	 indicated  by	event  and  return its
	      result.  Event defaults to -1.  This command results in  history
	      revision:	 see below for details.

HISTORY REVISION
       Pre-8.0	Tcl  had  a  complex  history revision mechanism.  The current
       mechanism is more limited, and the old  history	operations  substitute
       and  words  have	 been removed.	(As a consolation, the clear operation
       was added.)

       The history option redo results in much simpler	``history  revision''.
       When  this  option is invoked then the most recent event is modified to
       eliminate the history command and replace it with  the  result  of  the
       history	command.   If you want to redo an event without modifying his‐
       tory, then use the event operation to retrieve some event, and the  add
       operation to add it to history and execute it.

KEYWORDS
       event, history, record

Tcl								    history(n)
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