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 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
              abbreviated)  then  the  command  is  also  executed  and  its result is returned.  If exec is not
              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 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 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 operation to add it to history and execute it.

KEYWORDS

       event, history, record

Tcl                                                                                                history(3tcl)