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<h4 class="subsection">2.4.5 Commands For Manipulating The History</h4>
<p><a name="index-command-history-129"></a><a name="index-input-history-130"></a><a name="index-history-of-commands-131"></a>
Octave normally keeps track of the commands you type so that you can
recall previous commands to edit or execute them again. When you exit
Octave, the most recent commands you have typed, up to the number
specified by the variable <code>history_size</code>, are saved in a file.
When Octave starts, it loads an initial list of commands from the file
named by the variable <code>history_file</code>.
<p>Here are the commands for simple browsing and searching the history
list.
<dl>
<dt><kbd><LFD></kbd><dt><kbd><RET></kbd><dd>Accept the current line regardless of where the cursor is. If the line is
non-empty, add it to the history list. If the line was a history
line, then restore the history line to its original state.
<br><dt><kbd>C-p</kbd><dd>Move `up' through the history list.
<br><dt><kbd>C-n</kbd><dd>Move `down' through the history list.
<br><dt><kbd>M-<</kbd><dd>Move to the first line in the history.
<br><dt><kbd>M-></kbd><dd>Move to the end of the input history, i.e., the line you are entering!
<br><dt><kbd>C-r</kbd><dd>Search backward starting at the current line and moving `up' through
the history as necessary. This is an incremental search.
<br><dt><kbd>C-s</kbd><dd>Search forward starting at the current line and moving `down' through
the history as necessary.
</dl>
<p>On most terminals, you can also use the up and down arrow keys in place
of <kbd>C-p</kbd> and <kbd>C-n</kbd> to move through the history list.
<p>In addition to the keyboard commands for moving through the history
list, Octave provides three functions for viewing, editing, and
re-running chunks of commands from the history list.
<!-- history src/oct-hist.cc -->
<p><a name="doc_002dhistory"></a>
<div class="defun">
— Command: <b>history</b><var> options<a name="index-history-132"></a></var><br>
<blockquote><p>If invoked with no arguments, <code>history</code> displays a list of commands
that you have executed. Valid options are:
<dl>
<dt><code>-w </code><var>file</var><dd>Write the current history to the file <var>file</var>. If the name is
omitted, use the default history file (normally <samp><span class="file">~/.octave_hist</span></samp>).
<br><dt><code>-r </code><var>file</var><dd>Read the file <var>file</var>, appending its contents to the current
history list. If the name is omitted, use the default history file
(normally <samp><span class="file">~/.octave_hist</span></samp>).
<br><dt><var>n</var><dd>Display only the most recent <var>n</var> lines of history.
<br><dt><code>-q</code><dd>Don't number the displayed lines of history. This is useful for cutting
and pasting commands using the X Window System.
</dl>
<p>For example, to display the five most recent commands that you have
typed without displaying line numbers, use the command
<kbd>history -q 5</kbd>.
</p></blockquote></div>
<!-- edit_history src/oct-hist.cc -->
<p><a name="doc_002dedit_005fhistory"></a>
<div class="defun">
— Command: <b>edit_history</b> [<var>first</var>] [<var>last</var>]<var><a name="index-edit_005fhistory-133"></a></var><br>
<blockquote><p>If invoked with no arguments, <code>edit_history</code> allows you to edit the
history list using the editor named by the variable <samp><span class="env">EDITOR</span></samp><!-- /@w -->. The
commands to be edited are first copied to a temporary file. When you
exit the editor, Octave executes the commands that remain in the file.
It is often more convenient to use <code>edit_history</code> to define functions
rather than attempting to enter them directly on the command line.
By default, the block of commands is executed as soon as you exit the
editor. To avoid executing any commands, simply delete all the lines
from the buffer before exiting the editor.
<p>The <code>edit_history</code> command takes two optional arguments specifying
the history numbers of first and last commands to edit. For example,
the command
<pre class="example"> edit_history 13
</pre>
<p class="noindent">extracts all the commands from the 13th through the last in the history
list. The command
<pre class="example"> edit_history 13 169
</pre>
<p class="noindent">only extracts commands 13 through 169. Specifying a larger number for
the first command than the last command reverses the list of commands
before placing them in the buffer to be edited. If both arguments are
omitted, the previous command in the history list is used.
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<!-- A simple blank line produces the correct behavior. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002drun_005fhistory.html#doc_002drun_005fhistory">run_history</a>.
</p></blockquote></div>
<!-- run_history src/oct-hist.cc -->
<p><a name="doc_002drun_005fhistory"></a>
<div class="defun">
— Command: <b>run_history</b> [<var>first</var>] [<var>last</var>]<var><a name="index-run_005fhistory-134"></a></var><br>
<blockquote><p>Similar to <code>edit_history</code>, except that the editor is not invoked,
and the commands are simply executed as they appear in the history list.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dedit_005fhistory.html#doc_002dedit_005fhistory">edit_history</a>.
</p></blockquote></div>
<p class="noindent">Octave also allows you customize the details of when, where, and how history
is saved.
<!-- saving_history src/oct-hist.cc -->
<p><a name="doc_002dsaving_005fhistory"></a>
<div class="defun">
— Built-in Function: <var>val</var> = <b>saving_history</b> ()<var><a name="index-saving_005fhistory-135"></a></var><br>
— Built-in Function: <var>old_val</var> = <b>saving_history</b> (<var>new_val</var>)<var><a name="index-saving_005fhistory-136"></a></var><br>
— Built-in Function: <b>saving_history</b> (<var>new_val, "local"</var>)<var><a name="index-saving_005fhistory-137"></a></var><br>
<blockquote><p>Query or set the internal variable that controls whether commands entered
on the command line are saved in the history file.
<p>When called from inside a function with the "local" option, the variable is
changed locally for the function and any subroutines it calls. The original
variable value is restored when exiting the function.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dhistory_005fcontrol.html#doc_002dhistory_005fcontrol">history_control</a>, <a href="doc_002dhistory_005ffile.html#doc_002dhistory_005ffile">history_file</a>, <a href="doc_002dhistory_005fsize.html#doc_002dhistory_005fsize">history_size</a>, <a href="doc_002dhistory_005ftimestamp_005fformat_005fstring.html#doc_002dhistory_005ftimestamp_005fformat_005fstring">history_timestamp_format_string</a>.
</p></blockquote></div>
<!-- history_control src/oct-hist.cc -->
<p><a name="doc_002dhistory_005fcontrol"></a>
<div class="defun">
— Built-in Function: <var>val</var> = <b>history_control</b> ()<var><a name="index-history_005fcontrol-138"></a></var><br>
— Built-in Function: <var>old_val</var> = <b>history_control</b> (<var>new_val</var>)<var><a name="index-history_005fcontrol-139"></a></var><br>
<blockquote><p>Query or set the internal variable that specifies how commands are saved
to the history list. The default value is an empty character string,
but may be overridden by the environment variable
<samp><span class="env">OCTAVE_HISTCONTROL</span></samp><!-- /@w -->.
<p>The value of <code>history_control</code> is a colon-separated list of values
controlling how commands are saved on the history list. If the list
of values includes <code>ignorespace</code>, lines which begin with a space
character are not saved in the history list. A value of <code>ignoredups</code>
causes lines matching the previous history entry to not be saved.
A value of <code>ignoreboth</code> is shorthand for <code>ignorespace</code> and
<code>ignoredups</code>. A value of <code>erasedups</code> causes all previous lines
matching the current line to be removed from the history list before that
line is saved. Any value not in the above list is ignored. If
<code>history_control</code> is the empty string, all commands are saved on
the history list, subject to the value of <code>saving_history</code>.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dhistory_005ffile.html#doc_002dhistory_005ffile">history_file</a>, <a href="doc_002dhistory_005fsize.html#doc_002dhistory_005fsize">history_size</a>, <a href="doc_002dhistory_005ftimestamp_005fformat_005fstring.html#doc_002dhistory_005ftimestamp_005fformat_005fstring">history_timestamp_format_string</a>, <a href="doc_002dsaving_005fhistory.html#doc_002dsaving_005fhistory">saving_history</a>.
</p></blockquote></div>
<!-- history_file src/oct-hist.cc -->
<p><a name="doc_002dhistory_005ffile"></a>
<div class="defun">
— Built-in Function: <var>val</var> = <b>history_file</b> ()<var><a name="index-history_005ffile-140"></a></var><br>
— Built-in Function: <var>old_val</var> = <b>history_file</b> (<var>new_val</var>)<var><a name="index-history_005ffile-141"></a></var><br>
<blockquote><p>Query or set the internal variable that specifies the name of the
file used to store command history. The default value is
<samp><span class="file">~/.octave_hist</span></samp>, but may be overridden by the environment
variable <samp><span class="env">OCTAVE_HISTFILE</span></samp><!-- /@w -->.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
<!-- A simple blank line produces the correct behavior. -->
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dhistory_005fsize.html#doc_002dhistory_005fsize">history_size</a>, <a href="doc_002dsaving_005fhistory.html#doc_002dsaving_005fhistory">saving_history</a>, <a href="doc_002dhistory_005ftimestamp_005fformat_005fstring.html#doc_002dhistory_005ftimestamp_005fformat_005fstring">history_timestamp_format_string</a>.
</p></blockquote></div>
<!-- history_size src/oct-hist.cc -->
<p><a name="doc_002dhistory_005fsize"></a>
<div class="defun">
— Built-in Function: <var>val</var> = <b>history_size</b> ()<var><a name="index-history_005fsize-142"></a></var><br>
— Built-in Function: <var>old_val</var> = <b>history_size</b> (<var>new_val</var>)<var><a name="index-history_005fsize-143"></a></var><br>
<blockquote><p>Query or set the internal variable that specifies how many entries
to store in the history file. The default value is <code>1024</code>,
but may be overridden by the environment variable <samp><span class="env">OCTAVE_HISTSIZE</span></samp><!-- /@w -->.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
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<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dhistory_005ffile.html#doc_002dhistory_005ffile">history_file</a>, <a href="doc_002dhistory_005ftimestamp_005fformat_005fstring.html#doc_002dhistory_005ftimestamp_005fformat_005fstring">history_timestamp_format_string</a>, <a href="doc_002dsaving_005fhistory.html#doc_002dsaving_005fhistory">saving_history</a>.
</p></blockquote></div>
<!-- history_timestamp_format_string src/oct-hist.cc -->
<p><a name="doc_002dhistory_005ftimestamp_005fformat_005fstring"></a>
<div class="defun">
— Built-in Function: <var>val</var> = <b>history_timestamp_format_string</b> ()<var><a name="index-history_005ftimestamp_005fformat_005fstring-144"></a></var><br>
— Built-in Function: <var>old_val</var> = <b>history_timestamp_format_string</b> (<var>new_val</var>)<var><a name="index-history_005ftimestamp_005fformat_005fstring-145"></a></var><br>
— Built-in Function: <b>history_timestamp_format_string</b> (<var>new_val, "local"</var>)<var><a name="index-history_005ftimestamp_005fformat_005fstring-146"></a></var><br>
<blockquote><p>Query or set the internal variable that specifies the format string
for the comment line that is written to the history file when Octave
exits. The format string is passed to <code>strftime</code>. The default
value is
<pre class="example"> "# Octave VERSION, %a %b %d %H:%M:%S %Y %Z <USER@HOST>"
</pre>
<p>When called from inside a function with the "local" option, the variable is
changed locally for the function and any subroutines it calls. The original
variable value is restored when exiting the function.
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<p class="noindent"><strong>See also:</strong> <a href="doc_002dstrftime.html#doc_002dstrftime">strftime</a>, <a href="doc_002dhistory_005ffile.html#doc_002dhistory_005ffile">history_file</a>, <a href="doc_002dhistory_005fsize.html#doc_002dhistory_005fsize">history_size</a>, <a href="doc_002dsaving_005fhistory.html#doc_002dsaving_005fhistory">saving_history</a>.
</p></blockquote></div>
<!-- EDITOR src/defaults.cc -->
<p><a name="doc_002dEDITOR"></a>
<div class="defun">
— Built-in Function: <var>val</var> = <b>EDITOR</b> ()<var><a name="index-EDITOR-147"></a></var><br>
— Built-in Function: <var>old_val</var> = <b>EDITOR</b> (<var>new_val</var>)<var><a name="index-EDITOR-148"></a></var><br>
— Built-in Function: <b>EDITOR</b> (<var>new_val, "local"</var>)<var><a name="index-EDITOR-149"></a></var><br>
<blockquote><p>Query or set the internal variable that specifies the editor to
use with the <code>edit_history</code> command. The default value is taken from
the environment variable <samp><span class="env">EDITOR</span></samp><!-- /@w --> when Octave starts. If the
environment variable is not initialized, <samp><span class="env">EDITOR</span></samp><!-- /@w --> will be set to
<code>"emacs"</code>.
<p>When called from inside a function with the "local" option, the variable is
changed locally for the function and any subroutines it calls. The original
variable value is restored when exiting the function.
<!-- Texinfo @sp should work but in practice produces ugly results for HTML. -->
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<!-- @sp 1 -->
<p class="noindent"><strong>See also:</strong> <a href="doc_002dedit_005fhistory.html#doc_002dedit_005fhistory">edit_history</a>.
</p></blockquote></div>
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