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OpenDarwin 7.2.1 - man page for history (opendarwin section n)

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

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NAME
       history - Manipulate the history list

SYNOPSIS
       history ?option? ?arg arg ...?
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DESCRIPTION
       The  history  command performs one of several operations related to recently-executed com-
       mands 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 negative, 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 con-
	      sidered to match the string either if the string is the same as the  first  charac-
	      ters  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 commands 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 history 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 history 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 history list.  It is
	      useful for things like printing the event number 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 lim-
       ited, and the old history operations substitute and words have been removed.  (As a conso-
       lation, 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 history, then use the event operation to retrieve some event, and the add opera-
       tion to add it to history and execute it.

KEYWORDS
       event, history, record

Tcl										       history(n)
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