ch04_04.htm

by Randal L. Schwartz and Tom Phoenix ISBN 0-596-00132-0 Third Edition, published July 2001. (See

<dd>
<a name="INDEX-369" /><a name="INDEX-370" />The internal
flag that the debugger clears so that it doesn't
debug itself.
</p>
</dd>


<dt><b><tt class="literal">$^T</tt></b></dt>
<dt><b><tt class="literal">$BASETIME</tt></b></dt>
<dd>
<a name="INDEX-371" /><a name="INDEX-372" />The time at
which the script began running, in seconds since the epoch.
</p>
</dd>


<dt><b><tt class="literal">$^W</tt></b></dt>
<dt><b><tt class="literal">$WARNING</tt></b></dt>
<dd>
<a name="INDEX-373" /><a name="INDEX-374" />The current
value of the warning switch, either true or false.
</p>
</dd>


<dt><b><tt class="literal">$^X</tt></b></dt>
<dt><b><tt class="literal">$EXECUTABLE_NAME</tt></b></dt>
<dd>
<a name="INDEX-375" /><a name="INDEX-376" />The name that the Perl binary itself
was executed as. As of Perl 5.8, Perl asks the operating system
instead of using C's <tt class="literal">argv[0]</tt>.
</p>
</dd>


<dt><b><tt class="literal">$ARGV</tt></b></dt>
<dd>
<a name="INDEX-377" />Contains the name of the current file
when reading from <tt class="literal">&lt;ARGV&gt;</tt>.
</p>
</dd>

</dl>

</div>
<a name="perlnut2-CHP-4-SECT-4.2" /><div class="sect2">
<h3 class="sect2">4.4.2. Global Special Arrays and Hashes</h3>
<a name="INDEX-378" /><a name="INDEX-379" />
<dl>
<dt><b><tt class="literal">@ARGV</tt></b></dt>
<dd>
<a name="INDEX-380" />The array containing the command-line
arguments intended for the script.
</p>
</dd>


<dt><b><tt class="literal">@INC</tt></b></dt>
<dd>
<a name="INDEX-381" />The array containing the list of places to
look for Perl scripts to be evaluated by the <tt class="literal">do</tt>,
<tt class="literal">require</tt>, or <tt class="literal">use</tt> constructs.
</p>
</dd>


<dt><b><tt class="literal">@F</tt></b></dt>
<dd>
<a name="INDEX-382" />The array into which the input lines are
split when the <em class="emphasis">-a</em> command-line switch is given.
</p>
</dd>


<dt><b><tt class="literal">%INC</tt></b></dt>
<dd>
<a name="INDEX-383" />The hash containing entries for the
filename of each file that has been included via
<tt class="literal">do</tt> or <tt class="literal">require</tt>.
</p>
</dd>


<dt><b><tt class="literal">%ENV</tt></b></dt>
<dd>
<a name="INDEX-384" />The hash containing your current
environment.
</p>
</dd>


<dt><b><tt class="literal">%SIG</tt></b></dt>
<dd>
<a name="INDEX-385" />The hash used to set signal handlers for
various signals.
</p>
</dd>

</dl>

</div>
<a name="perlnut2-CHP-4-SECT-4.3" /><div class="sect2">
<h3 class="sect2">4.4.3. Global Special Filehandles</h3>
<a name="INDEX-386" />
<dl>
<dt><b><tt class="literal">ARGV</tt></b></dt>
<dd>
<a name="INDEX-387" />The special
filehandle that iterates over command-line filenames in
<tt class="literal">@ARGV</tt>. Usually written as the null filehandle in
<tt class="literal">&lt;&gt;</tt>.
</p>
</dd>


<dt><b><tt class="literal">STDERR</tt></b></dt>
<dd>
<a name="INDEX-388" />The
special filehandle for standard error in any package.
</p>
</dd>


<dt><b><tt class="literal">STDIN</tt></b></dt>
<dd>
<a name="INDEX-389" />The special
filehandle for standard input in any package.
</p>
</dd>


<dt><b><tt class="literal">STDOUT</tt></b></dt>
<dd>
<a name="INDEX-390" />The
special filehandle for standard output in any package.
</p>
</dd>


<dt><b><tt class="literal">DATA</tt></b></dt>
<dd>
<a name="INDEX-391" />The special
filehandle that refers to anything following the <tt class="literal">_ _END_
_</tt> token in the file containing the script. Or the special
filehandle for anything following the <tt class="literal">_ _DATA_ _</tt>
token in a required file, as long as you're reading
data in the same package <tt class="literal">_ _DATA_ _</tt> was found in.
</p>
</dd>


<dt><b><tt class="literal">_</tt> (underscore)</b></dt>
<dd>
<a name="INDEX-392" /><a name="INDEX-393" />The special
filehandle used to cache the information from the last
<tt class="literal">stat</tt>, <tt class="literal">lstat</tt>, or file test
operator.
</p>
</dd>

</dl>

</div>
<a name="perlnut2-CHP-4-SECT-4.4" /><div class="sect2">
<h3 class="sect2">4.4.4. Global Special Constants</h3>
<a name="INDEX-394" />
<dl>
<dt><b><tt class="literal">_  _END_  _</tt></b></dt>
<dd>
<a name="INDEX-395" /> <a name="INDEX-396" />Indicates the
logical end of your program. Any following text is ignored, but may
be read via the <tt class="literal">DATA</tt> filehandle.
</p>
</dd>


<dt><b><tt class="literal">_  _FILE_  _</tt></b></dt>
<dd>
<a name="INDEX-397" /> <a name="INDEX-398" />Represents the
filename at the point in your program where it's
used. Not interpolated into strings.
</p>
</dd>


<dt><b><tt class="literal">_  _LINE_  _</tt></b></dt>
<dd>
<a name="INDEX-399" /> <a name="INDEX-400" />Represents the
current line number. Not interpolated into strings.
</p>
</dd>


<dt><b><tt class="literal">_  _PACKAGE_  _</tt></b></dt>
<dd>
<a name="INDEX-401" /> <a name="INDEX-402" />Represents the current package name at
compile time, or undefined if there is no current package. Not
interpolated into strings.
</p>
</dd>

</dl>

</div>
<a name="perlnut2-CHP-4-SECT-4.5" /><div class="sect2">
<h3 class="sect2">4.4.5. Regular Expression Special Variables</h3>

<p><a name="INDEX-403" />For more information on
regular expressions, see <a href="ch04_06.htm#perlnut2-CHP-4-SECT-6">Section 4.6, "Regular Expressions"</a> later in this chapter.
</p>

<dl>
<dt><b><tt class="literal">$</tt><em class="replaceable">digit</em></b></dt>
<dd>
<a name="INDEX-404" />Contains the text matched by the
corresponding set of parentheses in the last pattern matched. For
example, <tt class="literal">$1</tt> matches whatever was contained in the
first set of parentheses in the previous regular expression.
</p>
</dd>



<dt><b><tt class="literal">$&amp;</tt></b></dt>
<dt><b><tt class="literal">$MATCH</tt></b></dt>
<dd>
<a name="INDEX-405" /><a name="INDEX-406" />The string
matched by the last successful pattern match.
</p>
</dd>


<dt><b><tt class="literal">$'</tt></b></dt>
<dt><b><tt class="literal">$PREMATCH</tt></b></dt>
<dd>
<a name="INDEX-407" /><a name="INDEX-408" />The string
preceding whatever was matched by the last successful pattern match.
</p>
</dd>


<dt><b><tt class="literal">$'</tt></b></dt>
<dt><b><tt class="literal">$POSTMATCH</tt></b></dt>
<dd>
<a name="INDEX-409" /><a name="INDEX-410" />The
string following whatever was matched by the last successful pattern
match.
</p>
</dd>


<dt><b><tt class="literal">$+</tt></b></dt>
<dt><b><tt class="literal">$LAST_PAREN_MATCH</tt></b></dt>
<dd>
<a name="INDEX-411" /><a name="INDEX-412" />The last bracket matched by the last
search pattern. This is useful if you don't know
which of a set of alternative patterns was matched. For example:
</p>


<blockquote><pre class="code">/Version: (.*)|Revision: (.*)/ &amp;&amp; ($rev = $+);</pre></blockquote></dd>


<a name="INDEX-413" /><dt><b><tt class="literal">$^N</tt></b></dt>
<dd>
The string matched by the most recently closed group. This is most
useful inside <tt class="literal">(?{</tt> . . . <tt class="literal">})</tt>
blocks for examining matched text. If you have multiple matches
denoted by parentheses, <tt class="literal">$^N</tt> can be used in lieu of
<tt class="literal">$1</tt>, <tt class="literal">$2</tt>, <tt class="literal">$3</tt>,
etc., so you don't have to manually count the number
of sets of parentheses that denote your matches. For example:
</p>


<blockquote><pre class="code">#!/usr/local/bin/perl -w

$words = "person|here";
$words =~ /(\w+)\|(\w+)/;
print $^N;   # Prints 'here'</pre></blockquote></dd>

</dl>

</div>
<a name="perlnut2-CHP-4-SECT-4.6" /><div class="sect2">
<h3 class="sect2">4.4.6. Filehandle Special Variables</h3>

<p><a name="INDEX-414" />Most of these variables apply
only when using formats. See <a href="ch04_11.htm#perlnut2-CHP-4-SECT-11">Section 4.11, "Unicode"</a> later in this chapter.
</p>

<dl>
<dt><b><tt class="literal">$|</tt></b></dt>
<dt><b><tt class="literal">$OUTPUT_AUTOFLUSH</tt></b></dt>
<dd>
<a name="INDEX-415" /><a name="INDEX-416" />If set to nonzero, forces an
<tt class="literal">fflush(3)</tt> after every <tt class="literal">write</tt> or
<tt class="literal">print</tt> on the currently selected output channel.
</p>
</dd>


<dt><b><tt class="literal">$%</tt></b></dt>
<dt><b><tt class="literal">$FORMAT_PAGE_NUMBER</tt></b></dt>
<dd>
<a name="INDEX-417" /><a name="INDEX-418" />The current page number of the
currently selected output channel.
</p>
</dd>


<dt><b><tt class="literal">$=</tt></b></dt>
<dt><b><tt class="literal">$FORMAT_LINES_PER_PAGE</tt></b></dt>
<dd>
<a name="INDEX-419" /><a name="INDEX-420" />The current page length (printable
lines) of the currently selected output channel. Default is 60.
</p>
</dd>


<dt><b><tt class="literal">$-</tt></b></dt>
<dt><b><tt class="literal">$FORMAT_LINES_LEFT</tt></b></dt>
<dd>
<a name="INDEX-421" /><a name="INDEX-422" />The number of lines left on the page of
the currently selected output channel.
</p>
</dd>


<dt><b><tt class="literal">$~</tt></b></dt>
<dt><b><tt class="literal">$FORMAT_NAME</tt></b></dt>
<dd>
<a name="INDEX-423" /><a name="INDEX-424" />The name of the current report format
for the currently selected output channel. Default is the name of the
filehandle.
</p>
</dd>


<dt><b><tt class="literal">$^</tt></b></dt>
<dt><b><tt class="literal">$FORMAT_TOP_NAME</tt></b></dt>
<dd>
<a name="INDEX-425" /><a name="INDEX-426" />The name of the current top-of-page
format for the currently selected output channel. Default is the name
of the filehandle with <tt class="literal">_TOP</tt> appended.
</p>
</dd>

</dl>

</div>


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