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history(3tcl) Tcl Built-In Commands history(3tcl) 





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:



  

  
Same as history info, described below.

  

  
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.

  

  
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.

  

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

  

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

  

  
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.

  

  
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.

  

  
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.

  

  
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