distrib/share/tcl/help/tcl/status/history

   1 NAME
   2        history - Manipulate the history list
   3
   4 SYNOPSIS
   5        history ?option? ?arg arg ...?
   6
   7
   8 DESCRIPTION
   9        The  history  command  performs  one  of  several operations related to
  10        recently-executed commands recorded in a history list.  Each  of  these
  11        recorded  commands  is referred to as an ``event''.  When specifying an
  12        event to the history command, the following forms may be used:
  13
  14        [1]    A number:  if positive, it refers to the event with that  number
  15               (all events are numbered starting at 1).  If the number is nega-
  16               tive, it selects an event relative  to  the  current  event  (-1
  17               refers  to the previous event, -2 to the one before that, and so
  18               on).  Event 0 refers to the current event.
  19
  20        [2]    A string:  selects  the  most  recent  event  that  matches  the
  21               string.   An  event  is considered to match the string either if
  22               the string is the same as the first characters of the event,  or
  23               if the string matches the event in the sense of the string match
  24               command.
  25
  26        The history command can take any of the following forms:
  27
  28        history
  29               Same as history info, described below.
  30
  31        history add command ?exec?
  32               Adds the command argument to the history list as  a  new  event.
  33               If  exec  is specified (or abbreviated) then the command is also
  34               executed and its result is returned.  If  exec  isn't  specified
  35               then an empty string is returned as result.
  36
  37        history change newValue ?event?
  38               Replaces  the  value recorded for an event with newValue.  Event
  39               specifies the event to replace,  and  defaults  to  the  current
  40               event  (not event -1).  This command is intended for use in com-
  41               mands that implement new forms of history substitution and  wish
  42               to  replace  the  current event (which invokes the substitution)
  43               with the command created through substitution.  The return value
  44               is an empty string.
  45
  46        history clear
  47               Erase  the  history  list.   The current keep limit is retained.
  48               The history event numbers are reset.
  49
  50        history event ?event?
  51               Returns the value of the event given by event.   Event  defaults
  52               to -1.
  53
  54        history info ?count?
  55               Returns  a formatted string (intended for humans to read) giving
  56               the event number and contents for each of the events in the his-
  57               tory  list except the current event.  If count is specified then
  58               only the most recent count events are returned.
  59
  60        history keep ?count?
  61               This command may be used to change the size of the history  list
  62               to  count events.  Initially, 20 events are retained in the his-
  63               tory list.  If count is not specified, the current keep limit is
  64               returned.
  65
  66        history nextid
  67               Returns  the number of the next event to be recorded in the his-
  68               tory list.  It is useful for things like printing the event num-
  69               ber in command-line prompts.
  70
  71        history redo ?event?
  72               Re-executes  the  command  indicated  by  event  and returns its
  73               result.  Event defaults to -1.  This command results in  history
  74               revision:  see below for details.
  75
  76 HISTORY REVISION
  77        Pre-8.0  Tcl  had  a  complex  history revision mechanism.  The current
  78        mechanism is more limited, and the old  history  operations  substitute
  79        and  words  have  been removed.  (As a consolation, the clear operation
  80        was added.)
  81
  82        The history option redo results in much simpler  ``history  revision''.
  83        When  this  option is invoked then the most recent event is modified to
  84        eliminate the history command and replace it with  the  result  of  the
  85        history  command.   If you want to redo an event without modifying his-
  86        tory, then use the event operation to retrieve some event, and the  add
  87        operation to add it to history and execute it.
  88
  89
  90 KEYWORDS