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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 ...?
____________________________________________________________________________________________________________

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 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  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 abbre-viated) abbreviated)
              viated)  then  the command is also executed and its result is returned.  If exec is not speci-fied specified
              fied 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 commands
              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 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 returns 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  opera-tion operation
       tion 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 operation to add it to history and execute it.

KEYWORDS
       event, history, record



Tcl                                                                                               history(n)