169 lines
6.4 KiB
Plaintext
169 lines
6.4 KiB
Plaintext
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'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) history.n 1.6 96/03/25 20:16:25
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'\"
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.so man.macros
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.TH history n "" Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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history \- Manipulate the history list
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.SH SYNOPSIS
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\fBhistory \fR?\fIoption\fR? ?\fIarg arg ...\fR?
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.BE
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.SH DESCRIPTION
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.PP
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The \fBhistory\fR command performs one of several operations related to
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recently-executed commands recorded in a history list. Each of
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these recorded commands is referred to as an ``event''. When
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specifying an event to the \fBhistory\fR command, the following
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forms may be used:
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.IP [1]
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A number: if positive, it refers to the event with
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that number (all events are numbered starting at 1). If the number
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is negative, it selects an event relative to the current event
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(\fB\-1\fR refers to the previous event, \fB\-2\fR to the one before that, and
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so on).
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.IP [2]
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A string: selects the most recent event that matches the string.
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An event is considered to match the string either if the string is
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the same as the first characters of the event, or if the string
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matches the event in the sense of the \fBstring match\fR command.
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.PP
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The \fBhistory\fR command can take any of the following forms:
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.TP
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\fBhistory\fR
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Same
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as \fBhistory info\fR, described below.
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.TP
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\fBhistory add\fI command \fR?\fBexec\fR?
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Adds the \fIcommand\fR argument to the history list as a new event. If
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\fBexec\fR is specified (or abbreviated) then the command is also
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executed and its result is returned. If \fBexec\fR isn't specified
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then an empty string is returned as result.
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.TP
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\fBhistory change\fI newValue\fR ?\fIevent\fR?
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Replaces the value recorded for an event with \fInewValue\fR. \fIEvent\fR
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specifies the event to replace, and
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defaults to the \fIcurrent\fR event (not event \fB\-1\fR). This command
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is intended for use in commands that implement new forms of history
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substitution and wish to replace the current event (which invokes the
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substitution) with the command created through substitution. The return
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value is an empty string.
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.TP
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\fBhistory event\fR ?\fIevent\fR?
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Returns the value of the event given by \fIevent\fR. \fIEvent\fR
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defaults to \fB\-1\fR. This command causes history revision to occur:
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see below for details.
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.TP
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\fBhistory info \fR?\fIcount\fR?
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Returns a formatted string (intended for humans to read) giving
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the event number and contents for each of the events in the history
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list except the current event. If \fIcount\fR is specified
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then only the most recent \fIcount\fR events are returned.
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.TP
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\fBhistory keep \fIcount\fR
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This command may be used to change the size of the history list to
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\fIcount\fR events. Initially, 20 events are retained in the history
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list. This command returns an empty string.
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.TP
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\fBhistory nextid\fR
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Returns the number of the next event to be recorded
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in the history list. It is useful for things like printing the
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event number in command-line prompts.
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.TP
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\fBhistory redo \fR?\fIevent\fR?
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Re-executes the command indicated by \fIevent\fR and return its result.
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\fIEvent\fR defaults to \fB\-1\fR. This command results in history
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revision: see below for details.
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.TP
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\fBhistory substitute \fIold new \fR?\fIevent\fR?
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Retrieves the command given by \fIevent\fR
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(\fB\-1\fR by default), replace any occurrences of \fIold\fR by
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\fInew\fR in the command (only simple character equality is supported;
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no wild cards), execute the resulting command, and return the result
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of that execution. This command results in history
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revision: see below for details.
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.TP
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\fBhistory words \fIselector\fR ?\fIevent\fR?
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Retrieves from the command given by \fIevent\fR (\fB\-1\fR by default)
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the words given by \fIselector\fR, and return those words in a string
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separated by spaces. The \fBselector\fR argument has three forms.
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If it is a single number then it selects the word given by that
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number (\fB0\fR for the command name, \fB1\fR for its first argument,
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and so on). If it consists of two numbers separated by a dash,
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then it selects all the arguments between those two. Otherwise
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\fBselector\fR is treated as a pattern; all words matching that
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pattern (in the sense of \fBstring match\fR) are returned. In
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the numeric forms \fB$\fR may be used
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to select the last word of a command.
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For example, suppose the most recent command in the history list is
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.RS
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.CS
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\fBformat {%s is %d years old} Alice [expr $ageInMonths/12]\fR
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.CE
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Below are some history commands and the results they would produce:
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.DS
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.ta 4c
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.fi
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.UL Command " "
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.UL Result
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.nf
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\fBhistory words $ [expr $ageInMonths/12]\fR
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\fBhistory words 1-2 {%s is %d years old} Alice\fR
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\fBhistory words *a*o* {%s is %d years old} [expr $ageInMonths/12]\fR
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.DE
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\fBHistory words\fR results in history revision: see below for details.
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.RE
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.SH "HISTORY REVISION"
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.PP
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The history options \fBevent\fR, \fBredo\fR, \fBsubstitute\fR,
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and \fBwords\fR result in ``history revision''.
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When one of these options is invoked then the current event
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is modified to eliminate the history command and replace it with
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the result of the history command.
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For example, suppose that the most recent command in the history
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list is
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.CS
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\fBset a [expr $b+2]\fR
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.CE
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and suppose that the next command invoked is one of the ones on
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the left side of the table below. The command actually recorded in
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the history event will be the corresponding one on the right side
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of the table.
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.ne 1.5c
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.DS
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.ta 4c
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.fi
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.UL "Command Typed" " "
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.UL "Command Recorded"
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.nf
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\fBhistory redo set a [expr $b+2]\fR
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\fBhistory s a b set b [expr $b+2]\fR
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\fBset c [history w 2] set c [expr $b+2]\fR
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.DE
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History revision is needed because event specifiers like \fB\-1\fR
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are only valid at a particular time: once more events have been
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added to the history list a different event specifier would be
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needed.
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History revision occurs even when \fBhistory\fR is invoked
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indirectly from the current event (e.g. a user types a command
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that invokes a Tcl procedure that invokes \fBhistory\fR): the
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top-level command whose execution eventually resulted in a
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\fBhistory\fR command is replaced.
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If you wish to invoke commands like \fBhistory words\fR without
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history revision, you can use \fBhistory event\fR to save the
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current history event and then use \fBhistory change\fR to
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restore it later.
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.SH KEYWORDS
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event, history, record, revision
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