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<h1 class="chapter"> 32. Runtime Environment </h1>

<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top"><a href="#SEC177">32.1 Introduction for Runtime Environment</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">  
</td></tr>
<tr><td align="left" valign="top"><a href="#SEC178">32.2 Interrupts</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">                  
</td></tr>
<tr><td align="left" valign="top"><a href="#SEC179">32.3 Functions and Variables for Runtime Environment</a></td><td>&nbsp;&nbsp;</td><td align="left" valign="top">  
</td></tr>
</table>

<p><a name="Item_003a-Introduction-for-Runtime-Environment"></a>
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<h2 class="section"> 32.1 Introduction for Runtime Environment </h2>

<p><code>maxima-init.mac</code> is a file which is loaded automatically when Maxima
starts.  You can use <code>maxima-init.mac</code> to customize your Maxima
environment.  <code>maxima-init.mac</code>, if it exists, is typically placed in the
directory named by <code>maxima_userdir</code>,
although it can be in any directory searched by the function <code>file_search</code>.
</p>
<p>Here is an example <code>maxima-init.mac</code> file:
</p>
<pre class="example">setup_autoload (&quot;specfun.mac&quot;, ultraspherical, assoc_legendre_p);
showtime:all;
</pre>
<p>In this example, <code>setup_autoload</code> tells Maxima to load the
specified file
(<code>specfun.mac</code>) if any of the functions (<code>ultraspherical</code>,
<code>assoc_legendre_p</code>) are called but not yet defined.
Thus you needn't remember to load the file before calling the functions.
</p>
<p>The statement <code>showtime: all</code> tells Maxima to set the <code>showtime</code>
variable.  The <code>maxima-init.mac</code> file can contain any other assignments or
other Maxima statements.
</p>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Session-management">Session management</a>
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<p><a name="Item_003a-Interrupts"></a>
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<h2 class="section"> 32.2 Interrupts </h2>

<p>The user can stop a time-consuming computation with the
^C (control-C) character.
The default action is to stop the computation
and print another user prompt.
In this case, it is not possible to restart a stopped computation.
</p>
<p>If the Lisp variable <code>*debugger-hook*</code> is set to <code>nil</code>, by executing
</p>
<pre class="example">:lisp (setq *debugger-hook* nil)
</pre>

<p>then upon receiving ^C, Maxima will enter the Lisp debugger,
and the user may use the debugger to inspect the Lisp environment.
The stopped computation can be restarted by entering
<code>continue</code> in the Lisp debugger.
The means of returning to Maxima from the Lisp debugger
(other than running the computation to completion)
is different for each version of Lisp.
</p>
<p>On Unix systems, the character ^Z (control-Z) causes Maxima
to stop altogether, and control is returned to the shell prompt.
The <code>fg</code> command causes Maxima
to resume from the point at which it was stopped.
</p>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Console-interaction">Console interaction</a>
</div>
</p>

<p><a name="Item_003a-Functions-and-Variables-for-Runtime-Environment"></a>
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<h2 class="section"> 32.3 Functions and Variables for Runtime Environment </h2>

<p><a name="maxima_005ftempdir"></a>
<a name="Item_003a-maxima_005ftempdir"></a>
</p><dl>
<dt><u>System variable:</u> <b>maxima_tempdir</b>
<a name="IDX1253"></a>
</dt>
<dd><p><code>maxima_tempdir</code> names the directory in which Maxima creates some temporary
files.  In particular, temporary files for plotting are created in
<code>maxima_tempdir</code>.
</p>
<p>The initial value of <code>maxima_tempdir</code> is the user's home directory, if
Maxima can locate it; otherwise Maxima makes a guess about a suitable directory.
</p>
<p><code>maxima_tempdir</code> may be assigned a string which names a directory.
</p>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Global-variables">Global variables</a>
</div>
</p></dd></dl>

<p><a name="maxima_005fuserdir"></a>
<a name="Item_003a-maxima_005fuserdir"></a>
</p><dl>
<dt><u>System variable:</u> <b>maxima_userdir</b>
<a name="IDX1254"></a>
</dt>
<dd><p><code>maxima_userdir</code> names a directory which Maxima searches to find Maxima and
Lisp files.  (Maxima searches some other directories as well;
<code>file_search_maxima</code> and <code>file_search_lisp</code> are the complete lists.)
</p>
<p>The initial value of <code>maxima_userdir</code> is a subdirectory of the user's home
directory, if Maxima can locate it; otherwise Maxima makes a guess about a
suitable directory.
</p>
<p><code>maxima_userdir</code> may be assigned a string which names a directory.
However, assigning to <code>maxima_userdir</code> does not automatically change
<code>file_search_maxima</code> and <code>file_search_lisp</code>;
those variables must be changed separately.
</p>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Global-variables">Global variables</a>
</div>
</p></dd></dl>

<p><a name="room"></a>
<a name="Item_003a-room"></a>
</p><dl>
<dt><u>Function:</u> <b>room</b><i> &nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>room</tt> () &nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>room</tt> (true) &nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>room</tt> (false)</i>
<a name="IDX1255"></a>
</dt>
<dd><p>Prints out a description of the state of storage and
stack management in Maxima.  <code>room</code> calls the Lisp function of 
the same name.
</p>
<ul>
<li>
<code>room ()</code> prints out a moderate description.
</li><li>
<code>room (true)</code> prints out a verbose description.
</li><li>
<code>room (false)</code> prints out a terse description.
</li></ul>

<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Debugging">Debugging</a>
</div>
</p></dd></dl>

<p><a name="sstatus"></a>
<a name="Item_003a-sstatus"></a>
</p><dl>
<dt><u>Function:</u> <b>sstatus</b><i> (<var>keyword</var>, <var>item</var>)</i>
<a name="IDX1256"></a>
</dt>
<dd><p>When <var>keyword</var> is the symbol <code>feature</code>, <var>item</var> is put on the list
of system features.  After <code>sstatus (keyword, item)</code> is executed,
<code>status (feature, item)</code> returns <code>true</code>.  If <var>keyword</var> is the
symbol <code>nofeature</code>, <var>item</var> is deleted from the list of system features.
This can be useful for package writers, to keep track of what features they have
loaded in.
</p>
<p>See also <code><a href="#status">status</a></code>.
</p>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Programming">Programming</a>
</div>
</p></dd></dl>

<p><a name="status"></a>
<a name="Item_003a-status"></a>
</p><dl>
<dt><u>Function:</u> <b>status</b><i> &nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>status</tt> (<code>feature</code>) &nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>status</tt> (<code>feature</code>, <var>item</var>)</i>
<a name="IDX1257"></a>
</dt>
<dd><p>Returns information about the presence or absence of certain system-dependent 
features.
</p>
<ul>
<li>
<code>status (feature)</code> returns a list of system features. These include Lisp 
version, operating system type, etc. The list may vary from one Lisp type to 
another.

</li><li> 
<code>status (feature, item)</code> returns <code>true</code> if <var>item</var> is on the
list of items returned by <code>status (feature)</code> and <code>false</code> otherwise.
<code>status</code> quotes the argument <var>item</var>. The quote-quote operator 
<code>''</code> defeats quotation. A feature whose name contains a special 
character, such as a hyphen, must be given as a string argument. For example,
<code>status (feature, &quot;ansi-cl&quot;)</code>.
</li></ul>

<p>See also <code><a href="#sstatus">sstatus</a></code>.
</p>
<p>The variable <code>features</code> contains a list of features which apply to 
mathematical expressions. See <code>features</code> and <code>featurep</code> for more 
information.
</p>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Programming">Programming</a>
</div>
</p></dd></dl>


<p><a name="system"></a>
<a name="Item_003a-system"></a>
</p><dl>
<dt><u>Function:</u> <b>system</b><i> (<var>command</var>)</i>
<a name="IDX1258"></a>
</dt>
<dd><p>Executes <var>command</var> as a separate process.  The command is passed to the
default shell for execution.  <code>system</code> is not supported by all operating
systems, but generally exists in Unix and Unix-like environments.
</p>
<p>Supposing <code>_hist.out</code> is a list of frequencies which you wish to plot as a
bar graph using <code>xgraph</code>.
</p>
<pre class="example">(%i1) (with_stdout(&quot;_hist.out&quot;,
           for i:1 thru length(hist) do (
             print(i,hist[i]))),
       system(&quot;xgraph -bar -brw .7 -nl &lt; _hist.out&quot;));
</pre>
<p>In order to make the plot be done in the background (returning control to
Maxima) and remove the temporary file after it is done do:
</p>
<pre class="example">system(&quot;(xgraph -bar -brw .7 -nl &lt; _hist.out;  rm -f _hist.out)&amp;&quot;)
</pre></dd></dl>

<p><a name="time"></a>
<a name="Item_003a-time"></a>
</p><dl>
<dt><u>Function:</u> <b>time</b><i> (%o1, %o2, %o3, &hellip;)</i>
<a name="IDX1259"></a>
</dt>
<dd><p>Returns a list of the times, in seconds, taken to compute the output lines
<code>%o1</code>, <code>%o2</code>, <code>%o3</code>, &hellip; The time returned is Maxima's
estimate of the internal computation time, not the elapsed time.  <code>time</code>
can only be applied to output line variables; for any other variables,
<code>time</code> returns <code>unknown</code>.
</p>
<p>Set <code>showtime: true</code> to make Maxima print out the computation time 
and elapsed time with each output line.
</p>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Debugging">Debugging</a>
</div>
</p></dd></dl>

<p><a name="timedate"></a>
<a name="Item_003a-timedate"></a>
</p><dl>
<dt><u>Function:</u> <b>timedate</b><i> &nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>timedate</tt> (<var>T</var>, <var>tz_offset</var>)</i>
<a name="IDX1260"></a>
</dt>
<dd><br><p>&nbsp;&nbsp;&nbsp;&nbsp;<tt>timedate</tt> (<var>T</var>)
<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>timedate</tt> () &nbsp;</p>
<p><code>timedate(<var>T</var>, <var>tz_offset</var>)</code> returns a string
representing the time <var>T</var> in the time zone <var>tz_offset</var>.
The string format is <code>YYYY-MM-DD HH:MM:SS.NNN[+|-]ZZ:ZZ</code>
(using as many digits as necessary to represent the fractional part)
if <var>T</var> has a nonzero fractional part,
or <code>YYYY-MM-DD HH:MM:SS[+|-]ZZ:ZZ</code> if its fractional part is zero.
</p>
<p><var>T</var> measures time, in seconds, since midnight, January 1, 1900,
in the GMT time zone.
</p>
<p><var>tz_offset</var> measures the offset of the time zone, in hours,
east (positive) or west (negative) of GMT.
<var>tz_offset</var> must be an integer, rational, or float between -24 and 24, inclusive.
If <var>tz_offset</var> is not a multiple of 1/60, 
it is rounded to the nearest multiple of 1/60.
</p>
<p><code>timedate(<var>T</var>)</code> is equivalent to <code>timedate(<var>T</var>, <var>tz_offset</var>)</code>
with <var>tz_offset</var> equal to the offset of the local time zone.
</p>
<p><code>timedate()</code> is equivalent to <code>timedate(absolute_real_time())</code>.
That is, it returns the current time in the local time zone.
</p>
<p>Example:
</p>
<p><code>timedate</code> with no argument returns a string representing the current time and date.
</p>
<pre class="example">(%i1) d : timedate ();
(%o1)                      2010-06-08 04:08:09+01:00
(%i2) print (&quot;timedate reports current time&quot;, d) $
timedate reports current time 2010-06-08 04:08:09+01:00
</pre>
<p><code>timedate</code> with an argument returns a string representing the argument.
</p>
<pre class="example">(%i1) timedate (0);
(%o1)                      1900-01-01 01:00:00+01:00
(%i2) timedate (absolute_real_time () - 7*24*3600);
(%o2)                      2010-06-01 04:19:51+01:00
</pre>
<p><code>timedate</code> with optional timezone offset.
</p>
<pre class="example">(%i1) timedate (1000000000, -9.5);
(%o1)               1931-09-09 16:16:40-09:30
</pre>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Time-and-date-functions">Time and date functions</a>
</div>
</p></dd></dl>

<p><a name="parse_005ftimedate"></a>
<a name="Item_003a-parse_005ftimedate"></a>
</p><dl>
<dt><u>Function:</u> <b>parse_timedate</b><i> &nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;<tt>parse_timedate</tt> (<var>S</var>)</i>
<a name="IDX1261"></a>
</dt>
<dd><p>Parses a string <var>S</var> representing a date or date and time of day
and returns the number of seconds since midnight, January 1, 1900 GMT.
If there is a nonzero fractional part, the value returned is a rational number,
otherwise, it is an integer.
<code>parse_timedate</code> returns <code>false</code>
if it cannot parse <var>S</var> according to any of the allowed formats.
</p>
<p>The string <var>S</var> must have one of the following formats,
optionally followed by a timezone designation:
</p>
<ul>
<li>
<code>YYYY-MM-DD[ T]hh:mm:ss[,.]nnn</code>
</li><li>
<code>YYYY-MM-DD[ T]hh:mm:ss</code>
</li><li>
<code>YYYY-MM-DD</code>
</li></ul>

<p>where the fields are year, month, day, hours, minutes, seconds, and fraction of a second,
and square brackets indicate acceptable alternatives.
The fraction may contain one or more digits.
</p>
<p>Except for the fraction of a second,
each field must have exactly the number of digits indicated:
four digits for the year, and two for the month, day of the month, hours, minutes, and seconds.
</p>
<p>A timezone designation must have one of the following forms:
</p>
<ul>
<li>
<code>[+-]hh:mm</code>
</li><li>
<code>[+-]hhmm</code>
</li><li>
<code>[+-]hh</code>
</li><li>
<code>Z</code>
</li></ul>

<p>where <code>hh</code> and <code>mm</code> indicate hours and minutes east (<code>+</code>) or west (<code>-</code>) of GMT.
The timezone may be from +24 hours (inclusive) to -24 hours (inclusive).
</p>
<p>A literal character <code>Z</code> is equivalent to <code>+00:00</code> and its variants,
indicating GMT.
</p>
<p>If no timezone is indicated,
the time is assumed to be in the local time zone.
</p>
<p>Any leading or trailing whitespace (space, tab, newline, and carriage return) is ignored,
but any other leading or trailing characters cause <code>parse_timedate</code> to fail and return <code>false</code>.
</p>
<p>See also <code><a href="#timedate">timedate</a></code> and <code><a href="#absolute_005freal_005ftime">absolute_real_time</a></code>.
</p>
<p>Examples:
</p>
<p>Midnight, January 1, 1900, in the local time zone, in each acceptable format.
The result is the number of seconds the local time zone
is ahead (negative result) or behind (positive result) GMT.
In this example, the local time zone is 8 hours behind GMT.
</p>
<pre class="example">(%i1) parse_timedate (&quot;1900-01-01 00:00:00,000&quot;);
(%o1)                         28800
(%i2) parse_timedate (&quot;1900-01-01 00:00:00.000&quot;);
(%o2)                         28800
(%i3) parse_timedate (&quot;1900-01-01T00:00:00,000&quot;);
(%o3)                         28800
(%i4) parse_timedate (&quot;1900-01-01T00:00:00.000&quot;);
(%o4)                         28800
(%i5) parse_timedate (&quot;1900-01-01 00:00:00&quot;);
(%o5)                         28800
(%i6) parse_timedate (&quot;1900-01-01T00:00:00&quot;);
(%o6)                         28800
(%i7) parse_timedate (&quot;1900-01-01&quot;);
(%o7)                         28800
</pre>
<p>Midnight, January 1, 1900, GMT, in different indicated time zones.
</p>
<pre class="example">(%i1) parse_timedate (&quot;1900-01-01 19:00:00+19:00&quot;);
(%o1)                           0
(%i2) parse_timedate (&quot;1900-01-01 07:00:00+07:00&quot;);
(%o2)                           0
(%i3) parse_timedate (&quot;1900-01-01 01:00:00+01:00&quot;);
(%o3)                           0
(%i4) parse_timedate (&quot;1900-01-01Z&quot;);
(%o4)                           0
(%i5) parse_timedate (&quot;1899-12-31 21:00:00-03:00&quot;);
(%o5)                           0
(%i6) parse_timedate (&quot;1899-12-31 13:00:00-11:00&quot;);
(%o6)                           0
(%i7) parse_timedate (&quot;1899-12-31 08:00:00-16:00&quot;);
(%o7)                           0
</pre>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Time-and-date-functions">Time and date functions</a>
</div>
</p></dd></dl>

<p><a name="absolute_005freal_005ftime"></a>
<a name="Item_003a-absolute_005freal_005ftime"></a>
</p><dl>
<dt><u>Function:</u> <b>absolute_real_time</b><i> ()</i>
<a name="IDX1262"></a>
</dt>
<dd><p>Returns the number of seconds since midnight, January 1, 1900 GMT.
The return value is an integer.
</p>
<p>See also <code><a href="#elapsed_005freal_005ftime">elapsed_real_time</a></code> and <code><a href="#elapsed_005frun_005ftime">elapsed_run_time</a></code>.
</p>
<p>Example:
</p>
<pre class="example">(%i1) absolute_real_time ();
(%o1)                      3385045277
(%i2) 1900 + absolute_real_time () / (365.25 * 24 * 3600);
(%o2)                   2007.265612087104
</pre>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Time-and-date-functions">Time and date functions</a>
</div>
</p></dd></dl>

<p><a name="elapsed_005freal_005ftime"></a>
<a name="Item_003a-elapsed_005freal_005ftime"></a>
</p><dl>
<dt><u>Function:</u> <b>elapsed_real_time</b><i> ()</i>
<a name="IDX1263"></a>
</dt>
<dd><p>Returns the number of seconds (including fractions of a second)
since Maxima was most recently started or restarted.
The return value is a floating-point number.
</p>
<p>See also <code><a href="#absolute_005freal_005ftime">absolute_real_time</a></code> and <code><a href="#elapsed_005frun_005ftime">elapsed_run_time</a></code>.
</p>
<p>Example:
</p>
<pre class="example">(%i1) elapsed_real_time ();
(%o1)                       2.559324
(%i2) expand ((a + b)^500)$
(%i3) elapsed_real_time ();
(%o3)                       7.552087
</pre>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Time-and-date-functions">Time and date functions</a>
</div>
</p></dd></dl>

<p><a name="elapsed_005frun_005ftime"></a>
<a name="Item_003a-elapsed_005frun_005ftime"></a>
</p><dl>
<dt><u>Function:</u> <b>elapsed_run_time</b><i> ()</i>
<a name="IDX1264"></a>
</dt>
<dd><p>Returns an estimate of the number of seconds (including fractions of a second)
which Maxima has spent in computations since Maxima was most recently started
or restarted.  The return value is a floating-point number.
</p>
<p>See also <code><a href="#absolute_005freal_005ftime">absolute_real_time</a></code> and <code><a href="#elapsed_005freal_005ftime">elapsed_real_time</a></code>.
</p>
<p>Example:
</p>
<pre class="example">(%i1) elapsed_run_time ();
(%o1)                         0.04
(%i2) expand ((a + b)^500)$
(%i3) elapsed_run_time ();
(%o3)                         1.26
</pre>
<div class=categorybox>

<p>Categories:&nbsp;&nbsp;<a href="maxima_105.html#Category_003a-Time-and-date-functions">Time and date functions</a>
</div>
</p></dd></dl>


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