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 his
tory 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 new
Value. Event specifies the event to replace, and
defaults to the current event (not event -1). This
command is intended for use in commands that imple
ment new forms of history substitution and wish to
replace the current event (which invokes the sub
stitution) with the command created through substi
tution. The return value is an empty string.
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 cur
rent 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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