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- '\" $Header: /user6/ouster/tcl/man/RCS/history.n,v 1.1 93/05/03 17:09:47 ouster Exp $ SPRITE (Berkeley)
- '\"
- .\" The definitions below are for supplemental macros used in Tcl/Tk
- .\" manual entries.
- .\"
- .\" .HS name section [date [version]]
- .\" Replacement for .TH in other man pages. See below for valid
- .\" section names.
- .\"
- .\" .AP type name in/out [indent]
- .\" Start paragraph describing an argument to a library procedure.
- .\" type is type of argument (int, etc.), in/out is either "in", "out",
- .\" or "in/out" to describe whether procedure reads or modifies arg,
- .\" and indent is equivalent to second arg of .IP (shouldn't ever be
- .\" needed; use .AS below instead)
- .\"
- .\" .AS [type [name]]
- .\" Give maximum sizes of arguments for setting tab stops. Type and
- .\" name are examples of largest possible arguments that will be passed
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- .\"
- '\" # Heading for Tcl/Tk man pages
- .de HS
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- .\}
- .if \\n(^v \{\
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- ..
- .HS history tcl
- .BS
- '\" Note: do not modify the .SH NAME line immediately below!
- .SH NAME
- history \- Manipulate the history list
- .SH SYNOPSIS
- \fBhistory \fR?\fIoption\fR? ?\fIarg arg ...\fR?
- .BE
-
- .SH DESCRIPTION
- .PP
- The \fBhistory\fR 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 \fBhistory\fR command, the following
- forms may be used:
- .IP [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
- (\fB\-1\fR refers to the previous event, \fB\-2\fR to the one before that, and
- so on).
- .IP [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 \fBstring match\fR command.
- .LP
- The \fBhistory\fR command can take any of the following forms:
- .TP
- \fBhistory\fR
- Same
- as \fBhistory info\fR, described below.
- .TP
- \fBhistory add\fI command \fR?\fBexec\fR?
- Adds the \fIcommand\fR argument to the history list as a new event. If
- \fBexec\fR is specified (or abbreviated) then the command is also
- executed and its result is returned. If \fBexec\fR isn't specified
- then an empty string is returned as result.
- .TP
- \fBhistory change\fI newValue\fR ?\fIevent\fR?
- Replaces the value recorded for an event with \fInewValue\fR. \fIEvent\fR
- specifies the event to replace, and
- defaults to the \fIcurrent\fR event (not event \fB\-1\fR). 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.
- .TP
- \fBhistory event\fR ?\fIevent\fR?
- Returns the value of the event given by \fIevent\fR. \fIEvent\fR
- defaults to \fB\-1\fR. This command causes history revision to occur:
- see below for details.
- .TP
- \fBhistory info \fR?\fIcount\fR?
- 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 \fIcount\fR is specified
- then only the most recent \fIcount\fR events are returned.
- .TP
- \fBhistory keep \fIcount\fR
- This command may be used to change the size of the history list to
- \fIcount\fR events. Initially, 20 events are retained in the history
- list. This command returns an empty string.
- .TP
- \fBhistory nextid\fR
- 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.
- .TP
- \fBhistory redo \fR?\fIevent\fR?
- Re-executes the command indicated by \fIevent\fR and return its result.
- \fIEvent\fR defaults to \fB\-1\fR. This command results in history
- revision: see below for details.
- .TP
- \fBhistory substitute \fIold new \fR?\fIevent\fR?
- Retrieves the command given by \fIevent\fR
- (\fB\-1\fR by default), replace any occurrences of \fIold\fR by
- \fInew\fR 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.
- .TP
- \fBhistory words \fIselector\fR ?\fIevent\fR?
- Retrieves from the command given by \fIevent\fR (\fB\-1\fR by default)
- the words given by \fIselector\fR, and return those words in a string
- separated by spaces. The \fBselector\fR argument has three forms.
- If it is a single number then it selects the word given by that
- number (\fB0\fR for the command name, \fB1\fR 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
- \fBselector\fR is treated as a pattern; all words matching that
- pattern (in the sense of \fBstring match\fR) are returned. In
- the numeric forms \fB$\fR may be used
- to select the last word of a command.
- For example, suppose the most recent command in the history list is
- .RS
- .DS
- \fBformat {%s is %d years old} Alice [expr $ageInMonths/12]\fR
- .DE
- Below are some history commands and the results they would produce:
- .DS
- .ta 4c
- .fi
- .UL Command " "
- .UL Result
- .nf
-
- \fBhistory words $ [expr $ageInMonths/12]\fR
- \fBhistory words 1-2 {%s is %d years old} Alice\fR
- \fBhistory words *a*o* {%s is %d years old} [expr $ageInMonths/12]\fR
- .DE
- \fBHistory words\fR results in history revision: see below for details.
- .RE
- .SH "HISTORY REVISION"
- .PP
- The history options \fBevent\fR, \fBredo\fR, \fBsubstitute\fR,
- and \fBwords\fR 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
- .DS
- \fBset a [expr $b+2]\fR
- .DE
- 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.
- .ne 1.5c
- .DS
- .ta 4c
- .fi
- .UL "Command Typed" " "
- .UL "Command Recorded"
- .nf
-
- \fBhistory redo set a [expr $b+2]\fR
- \fBhistory s a b set b [expr $b+2]\fR
- \fBset c [history w 2] set c [expr $b+2]\fR
- .DE
- History revision is needed because event specifiers like \fB\-1\fR
- 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 \fBhistory\fR is invoked
- indirectly from the current event (e.g. a user types a command
- that invokes a Tcl procedure that invokes \fBhistory\fR): the
- top-level command whose execution eventually resulted in a
- \fBhistory\fR command is replaced.
- If you wish to invoke commands like \fBhistory words\fR without
- history revision, you can use \fBhistory event\fR to save the
- current history event and then use \fBhistory change\fR to
- restore it later.
-
- .SH KEYWORDS
- event, history, record, revision
-