history(n) Tcl 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 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 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.
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history(n) Tcl history(n)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 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
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