- NAME
- history - Manipulate the history list
- SYNOPSIS
- history ?option? ?arg arg ...?
- DESCRIPTION
- history
- history add command ?exec?
- history change newValue ?event?
- history event ?event?
- history info ?count?
- history keep count
- history nextid
- history redo ?event?
- history substitute old new ?event?
- history words selector ?event?
- HISTORY REVISION
- KEYWORDS
history - Manipulate the history list
history ?option? ?arg arg ...?
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).
- [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.
- history event ?event?
-
Returns the value of the event given by event. Event
defaults to -1. This command causes history revision to occur:
see below for details.
- 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. This command returns an empty string.
- 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 substitute old new ?event?
-
Retrieves the command given by event
(-1 by default), replace any occurrences of old by
new in the command (only simple character equality is supported;
no wild cards), execute the resulting command, and return the result
of that execution. This command results in history
revision: see below for details.
- history words selector ?event?
-
Retrieves from the command given by event (-1 by default)
the words given by selector, and return those words in a string
separated by spaces. The selector argument has three forms.
If it is a single number then it selects the word given by that
number (0 for the command name, 1 for its first argument,
and so on). If it consists of two numbers separated by a dash,
then it selects all the arguments between those two. Otherwise
selector is treated as a pattern; all words matching that
pattern (in the sense of string match) are returned. In
the numeric forms $ may be used
to select the last word of a command.
For example, suppose the most recent command in the history list is
format {%s is %d years old} Alice [expr $ageInMonths/12]
Below are some history commands and the results they would produce:
CommandResult
history words $ [expr $ageInMonths/12]
history words 1-2 {%s is %d years old} Alice
history words *a*o* {%s is %d years old} [expr $ageInMonths/12]
History words results in history revision: see below for details.
The history options event, redo, substitute,
and words result in ``history revision''.
When one of these options is invoked then the current event
is modified to eliminate the history command and replace it with
the result of the history command.
For example, suppose that the most recent command in the history
list is
set a [expr $b+2]
and suppose that the next command invoked is one of the ones on
the left side of the table below. The command actually recorded in
the history event will be the corresponding one on the right side
of the table.
CommandCommand
history redo set a [expr $b+2]
history s a b set b [expr $b+2]
set c [history w 2] set c [expr $b+2]
History revision is needed because event specifiers like -1
are only valid at a particular time: once more events have been
added to the history list a different event specifier would be
needed.
History revision occurs even when history is invoked
indirectly from the current event (e.g. a user types a command
that invokes a Tcl procedure that invokes history): the
top-level command whose execution eventually resulted in a
history command is replaced.
If you wish to invoke commands like history words without
history revision, you can use history event to save the
current history event and then use history change to
restore it later.
event, history, record, revision
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.
Copyright © 1995, 1996 Roger E. Critchlow Jr.