ch15.htm

美国Macmillan出版社编写的Perl教程《Perl CGI Web Pages for WINNT》

</blockquote>
<p>
<CENTER>
<TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=80%>
<TR VALIGN=TOP><TD WIDTH=605><B>NOTE</B></TD></TR>
<TR VALIGN=TOP><TD WIDTH=605>
<BLOCKQUOTE>
<I>Dynaloader has not been implemented in Windows NT Perl 5, so that any extension which requires dynamic loading cannot be supported.</I>
</BLOCKQUOTE>

</TD></TR>
</TABLE></CENTER>
<P>
<H2><A NAME="AssociativityandPrecedenceofOperatorsfromHighesttoLowest"><FONT SIZE=5 COLOR=#FF0000>
Associativity and Precedence of Operators from Highest to
Lowest</FONT></A></H2>

<P>
<CENTER>
<TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=80%>
<TR VALIGN=TOP><TD WIDTH=459><B>Operator</B></TD><TD WIDTH=117><B>Associativity</B>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>++ -- (Autoincrement, autodecrement)</TD><TD WIDTH=117>Right
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>! ~ - (Logical not, bitwise not, numeric negate)
</TD><TD WIDTH=117>Right</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>** (Exponentiation)</TD><TD WIDTH=117>Left</TD>
</TR>
<TR VALIGN=TOP><TD WIDTH=459>=~ !~ (Match, doesn't match)</TD><TD WIDTH=117>Left
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>* / % x (Multiply, divide, modulus, string repetition)
</TD><TD WIDTH=117>Left</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>+ - . (Add, subtract, string concatenate)</TD>
<TD WIDTH=117>Left</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>&lt;&lt; &gt;&gt; (Ait shift)</TD><TD WIDTH=117>None
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>-r and other file test operators (Note: use hex() and oct() to interpret hex and octal values)
</TD><TD WIDTH=117>None</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>The named unary operators</TD><TD WIDTH=117>None
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>&lt; &lt;= &gt; &gt;= lt le gt ge (The &quot;not equal&quot; operators)
</TD><TD WIDTH=117>None</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>== != &lt;=&gt; eq ne cmp (The &quot;equal&quot; operators)
</TD><TD WIDTH=117>Left</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>&amp; (Bitwise and)</TD><TD WIDTH=117>Left 
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>| ^ (Bitwise or, bitwise exclusive or)</TD>
<TD WIDTH=117>Left</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>&amp;&amp; (Logical and)</TD><TD WIDTH=117>Left
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>|| (Logical or)</TD><TD WIDTH=117>None</TD>
</TR>
<TR VALIGN=TOP><TD WIDTH=459>.. (Range operator, list constructor)</TD><TD WIDTH=117>Right
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>?: (Ternary if/then/else operator)</TD><TD WIDTH=117>Right
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>+= And others (the &quot;assignment&quot; operators)
</TD><TD WIDTH=117>Left</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>, (comma)</TD><TD WIDTH=117>None</TD></TR>
<TR VALIGN=TOP><TD WIDTH=459>The &quot;list&quot; operators</TD><TD WIDTH=117>&nbsp;
</TD></TR>
</TABLE></CENTER>
<P>
<H2><A NAME="PredefinedCharacterClassAbbreviations"><FONT SIZE=5 COLOR=#FF0000>
Predefined Character Class Abbreviations</FONT></A></H2>

<P>
<CENTER>
<TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=80%>
<TR VALIGN=TOP><TD WIDTH=125><B>Equivalent Class</B></TD><TD WIDTH=125><B>Construct</B>
</TD><TD WIDTH=125><B>Negated Class</B></TD><TD WIDTH=144><B>Negated Construct </B>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=125>\d (digits)</TD><TD WIDTH=125>[0-9]</TD><TD WIDTH=125>\D (digits, not!)
</TD><TD WIDTH=144>[^0-9]</TD></TR>
<TR VALIGN=TOP><TD WIDTH=125>\w (words)</TD><TD WIDTH=125>[a - zA - Z0-9_]
</TD><TD WIDTH=125>\W (words, not!)</TD><TD WIDTH=144>[^a - zA - Z0-9_]
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=125>\s (space)</TD><TD WIDTH=125>[ \r\t\n\f]</TD>
<TD WIDTH=125>\S (space, not!)</TD><TD WIDTH=144>[^ \r\t\n\f]
</TD></TR>
</TABLE></CENTER>
<P>
<H2><A NAME="RegularExpressionGroupingOperatorPrecedenceHighesttoLowest"><FONT SIZE=5 COLOR=#FF0000>
Regular Expression Grouping Operator Precedence-Highest to
Lowest</FONT></A></H2>

<P>
<CENTER>
<TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=60%>
<TR VALIGN=TOP><TD WIDTH=179><B>Name</B></TD><TD WIDTH=128><B>Representation</B>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=179>Parentheses</TD><TD WIDTH=128>()</TD></TR>
<TR VALIGN=TOP><TD WIDTH=179>Multipliers</TD><TD WIDTH=128>+ * ? {m,n}</TD>
</TR>
<TR VALIGN=TOP><TD WIDTH=179>Sequence and anchoring</TD><TD WIDTH=128>abc ^ $ \b \B
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=179>Alternation</TD><TD WIDTH=128>|</TD></TR>
</TABLE></CENTER>
<P>
<H2><A NAME="FileTests"><FONT SIZE=5 COLOR=#FF0000>
File Tests</FONT></A></H2>

<P>
<CENTER>
<TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=60%>
<TR VALIGN=TOP><TD WIDTH=96><CENTER><B>-r</B></CENTER></TD><TD WIDTH=384><B>File or directory is readable</B>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-w</CENTER></TD><TD WIDTH=384>File or directory is writable
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-x</CENTER></TD><TD WIDTH=384>File or directory is excutable
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-o</CENTER></TD><TD WIDTH=384>File or directory is owned by user
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-R</CENTER></TD><TD WIDTH=384>File or directory is readable by real user, not effective user
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-W</CENTER></TD><TD WIDTH=384>File or directory is writable by real user, not effective user
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-X</CENTER></TD><TD WIDTH=384>File or directory is writable by real user, not effective user
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-O</CENTER></TD><TD WIDTH=384>File or directory is owned by real user, not effective user
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-e</CENTER></TD><TD WIDTH=384>File or directory exists
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-z</CENTER></TD><TD WIDTH=384>File exists and has zero size
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-s</CENTER></TD><TD WIDTH=384>File or directory exists and has nonzero size
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-f</CENTER></TD><TD WIDTH=384>Entry is plain file
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-d</CENTER></TD><TD WIDTH=384>Entry is a directory
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-l</CENTER></TD><TD WIDTH=384>Entry is a symlink
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-S</CENTER></TD><TD WIDTH=384>Entry is a socket
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-p</CENTER></TD><TD WIDTH=384>Entry is a pipe
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-b</CENTER></TD><TD WIDTH=384>Entry is a block-special file
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-c</CENTER></TD><TD WIDTH=384>Entry is a character-special file
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-u</CENTER></TD><TD WIDTH=384>File or directory is setuid
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-g</CENTER></TD><TD WIDTH=384>File or directory is setgid
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-k</CENTER></TD><TD WIDTH=384>File or directory has the sticky bit set
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-t</CENTER></TD><TD WIDTH=384>Isatty() on the filehandle true
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-T</CENTER></TD><TD WIDTH=384>File is text
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-B</CENTER></TD><TD WIDTH=384>File is binary
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-M</CENTER></TD><TD WIDTH=384>Modification age in days
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-A</CENTER></TD><TD WIDTH=384>Access age in days
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=96><CENTER>-C</CENTER></TD><TD WIDTH=384>Inode-modification age in days
</TD></TR>
</TABLE></CENTER>
<P>
<H2><A NAME="PerlGNUGeneralPublicLicense"><FONT SIZE=5 COLOR=#FF0000>
Perl GNU General Public License</FONT></A></H2>
<P>
Version 2, June 1991
<P>
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
<P>
675 Mass Ave, Cambridge, MA 02139, USA
<P>
Everyone is permitted to copy and distribute verbatim copies of
this license document, but changing it is not allowed.
<H3><A NAME="Preamble1">
Preamble</A></H3>
<P>
The licenses for most software are designed to take away your
freedom to share and change it. By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change
free software-to make sure the software is free for all its users.
This General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit
to using it. (Some other Free Software Foundation software is
covered by the GNU Library General Public License instead.) You
can apply it to your programs, too.
<P>
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that
you have the freedom to distribute copies of free software (and
charge for this service if you wish), that you receive source
code or can get it if you want it, that you can change the software
or use pieces of it in new free programs; and that you know you
can do these things.
<P>
To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the
rights.
<P>
These restrictions translate to certain responsibilities for you
if you distribute copies of the software, or if you modify it.
<P>
For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights
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<P>
We protect your rights with two steps: (1) copyright the software,
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<P>
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<P>
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<P>
The precise terms and conditions for copying, distribution and
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<H2><A NAME="GNUGeneralPublicLicense"><FONT SIZE=5 COLOR=#FF0000>
GNU General Public License</FONT></A></H2>
<H3><A NAME="TermsandConditionsforCopyingDistributionandModification">
Terms and Conditions for Copying, Distribution, and Modification
</A></H3>
<P>

<TABLE CELLPADDING=5>
<TR VALIGN=TOP><TD>&nbsp;&nbsp;&nbsp;0</TD><TD>
This License applies to any program or other work which contains
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<OL>
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</OL>
<P>
<OL>
<OL TYPE=a>
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</OL>
</OL>
<P>

<OL START=3>
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<P>
<ol>
<OL type=a>
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