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perl教程

<dt><strong><a name="item_cp"><code>cp</code></a></strong>

<dd>
<p>From <em>Loc.U</em>:</p>
</dd>
<dd>
<p>This variable is used internally by Configure to determine the
full pathname (if any) of the cp program.  After Configure runs,
the value is reset to a plain <a href="#item_cp"><code>cp</code></a> and is not useful.</p>
</dd>
</li>
<dt><strong><a name="item_cpio"><code>cpio</code></a></strong>

<dd>
<p>From <em>Loc.U</em>:</p>
</dd>
<dd>
<p>This variable is defined but not used by Configure.
The value is a plain '' and is not useful.</p>
</dd>
</li>
<dt><strong><a name="item_cpp"><code>cpp</code></a></strong>

<dd>
<p>From <em>Loc.U</em>:</p>
</dd>
<dd>
<p>This variable is used internally by Configure to determine the
full pathname (if any) of the cpp program.  After Configure runs,
the value is reset to a plain <a href="#item_cpp"><code>cpp</code></a> and is not useful.</p>
</dd>
</li>
<dt><strong><a name="item_cpp_stuff"><code>cpp_stuff</code></a></strong>

<dd>
<p>From <em>cpp_stuff.U</em>:</p>
</dd>
<dd>
<p>This variable contains an identification of the concatenation mechanism
used by the C preprocessor.</p>
</dd>
</li>
<dt><strong><a name="item_cppccsymbols"><code>cppccsymbols</code></a></strong>

<dd>
<p>From <em>Cppsym.U</em>:</p>
</dd>
<dd>
<p>The variable contains the symbols defined by the C compiler
when it calls cpp.  The symbols defined by the cc alone or cpp
alone are not in this list, see ccsymbols and cppsymbols.
The list is a space-separated list of symbol=value tokens.</p>
</dd>
</li>
<dt><strong><a name="item_cppflags"><code>cppflags</code></a></strong>

<dd>
<p>From <em>ccflags.U</em>:</p>
</dd>
<dd>
<p>This variable holds the flags that will be passed to the C pre-
processor. It is up to the Makefile to use it.</p>
</dd>
</li>
<dt><strong><a name="item_cpplast"><code>cpplast</code></a></strong>

<dd>
<p>From <em>cppstdin.U</em>:</p>
</dd>
<dd>
<p>This variable has the same functionality as cppminus, only it applies
to cpprun and not cppstdin.</p>
</dd>
</li>
<dt><strong><a name="item_cppminus"><code>cppminus</code></a></strong>

<dd>
<p>From <em>cppstdin.U</em>:</p>
</dd>
<dd>
<p>This variable contains the second part of the string which will invoke
the C preprocessor on the standard input and produce to standard
output.  This variable will have the value <code>-</code> if cppstdin needs
a minus to specify standard input, otherwise the value is &quot;&quot;.</p>
</dd>
</li>
<dt><strong><a name="item_cpprun"><code>cpprun</code></a></strong>

<dd>
<p>From <em>cppstdin.U</em>:</p>
</dd>
<dd>
<p>This variable contains the command which will invoke a C preprocessor
on standard input and put the output to stdout. It is guaranteed not
to be a wrapper and may be a null string if no preprocessor can be
made directly available. This preprocessor might be different from the
one used by the C compiler. Don't forget to append cpplast after the
preprocessor options.</p>
</dd>
</li>
<dt><strong><a name="item_cppstdin"><code>cppstdin</code></a></strong>

<dd>
<p>From <em>cppstdin.U</em>:</p>
</dd>
<dd>
<p>This variable contains the command which will invoke the C
preprocessor on standard input and put the output to stdout.
It is primarily used by other Configure units that ask about
preprocessor symbols.</p>
</dd>
</li>
<dt><strong><a name="item_cppsymbols"><code>cppsymbols</code></a></strong>

<dd>
<p>From <em>Cppsym.U</em>:</p>
</dd>
<dd>
<p>The variable contains the symbols defined by the C preprocessor
alone.  The symbols defined by cc or by cc when it calls cpp are
not in this list, see ccsymbols and cppccsymbols.
The list is a space-separated list of symbol=value tokens.</p>
</dd>
</li>
<dt><strong><a name="item_crypt_r_proto"><code>crypt_r_proto</code></a></strong>

<dd>
<p>From <em>d_crypt_r.U</em>:</p>
</dd>
<dd>
<p>This variable encodes the prototype of crypt_r.
It is zero if d_crypt_r is undef, and one of the
<code>REENTRANT_PROTO_T_ABC</code> macros of <em>reentr.h</em> if d_crypt_r
is defined.</p>
</dd>
</li>
<dt><strong><a name="item_cryptlib"><code>cryptlib</code></a></strong>

<dd>
<p>From <em>d_crypt.U</em>:</p>
</dd>
<dd>
<p>This variable holds -lcrypt or the path to a <em>libcrypt.a</em> archive if
the <a href="../lib/Pod/perlfunc.html#item_crypt"><code>crypt()</code></a> function is not defined in the standard C library. It is
up to the Makefile to use this.</p>
</dd>
</li>
<dt><strong><a name="item_csh"><code>csh</code></a></strong>

<dd>
<p>From <em>Loc.U</em>:</p>
</dd>
<dd>
<p>This variable is used internally by Configure to determine the
full pathname (if any) of the csh program.  After Configure runs,
the value is reset to a plain <a href="#item_csh"><code>csh</code></a> and is not useful.</p>
</dd>
</li>
<dt><strong><a name="item_ctermid_r_proto"><code>ctermid_r_proto</code></a></strong>

<dd>
<p>From <em>d_ctermid_r.U</em>:</p>
</dd>
<dd>
<p>This variable encodes the prototype of ctermid_r.
It is zero if d_ctermid_r is undef, and one of the
<code>REENTRANT_PROTO_T_ABC</code> macros of <em>reentr.h</em> if d_ctermid_r
is defined.</p>
</dd>
</li>
<dt><strong><a name="item_ctime_r_proto"><code>ctime_r_proto</code></a></strong>

<dd>
<p>From <em>d_ctime_r.U</em>:</p>
</dd>
<dd>
<p>This variable encodes the prototype of ctime_r.
It is zero if d_ctime_r is undef, and one of the
<code>REENTRANT_PROTO_T_ABC</code> macros of <em>reentr.h</em> if d_ctime_r
is defined.</p>
</dd>
</li>
</dl>
<p>
</p>
<h2><a name="d">d</a></h2>
<dl>
<dt><strong><a name="item_d__fwalk"><code>d__fwalk</code></a></strong>

<dd>
<p>From <em>d__fwalk.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HAS__FWALK</code> if <code>_fwalk()</code> is
available to apply a function to all the file handles.</p>
</dd>
</li>
<dt><strong><a name="item_d_access"><code>d_access</code></a></strong>

<dd>
<p>From <em>d_access.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HAS_ACCESS</code> if the <code>access()</code> system
call is available to check for access permissions using real IDs.</p>
</dd>
</li>
<dt><strong><a name="item_d_accessx"><code>d_accessx</code></a></strong>

<dd>
<p>From <em>d_accessx.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_ACCESSX</code> symbol, which
indicates to the C program that the <code>accessx()</code> routine is available.</p>
</dd>
</li>
<dt><strong><a name="item_d_aintl"><code>d_aintl</code></a></strong>

<dd>
<p>From <em>d_aintl.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_AINTL</code> symbol, which
indicates to the C program that the <code>aintl()</code> routine is available.
If copysignl is also present we can emulate modfl.</p>
</dd>
</li>
<dt><strong><a name="item_d_alarm"><code>d_alarm</code></a></strong>

<dd>
<p>From <em>d_alarm.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_ALARM</code> symbol, which
indicates to the C program that the <a href="../lib/Pod/perlfunc.html#item_alarm"><code>alarm()</code></a> routine is available.</p>
</dd>
</li>
<dt><strong><a name="item_d_archlib"><code>d_archlib</code></a></strong>

<dd>
<p>From <em>archlib.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>ARCHLIB</code> to hold the pathname
of architecture-dependent library files for $package.  If
$archlib is the same as $privlib, then this is set to undef.</p>
</dd>
</li>
<dt><strong><a name="item_d_asctime_r"><code>d_asctime_r</code></a></strong>

<dd>
<p>From <em>d_asctime_r.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_ASCTIME_R</code> symbol,
which indicates to the C program that the <code>asctime_r()</code>
routine is available.</p>
</dd>
</li>
<dt><strong><a name="item_d_atolf"><code>d_atolf</code></a></strong>

<dd>
<p>From <em>atolf.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_ATOLF</code> symbol, which
indicates to the C program that the <code>atolf()</code> routine is available.</p>
</dd>
</li>
<dt><strong><a name="item_d_atoll"><code>d_atoll</code></a></strong>

<dd>
<p>From <em>atoll.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_ATOLL</code> symbol, which
indicates to the C program that the <code>atoll()</code> routine is available.</p>
</dd>
</li>
<dt><strong><a name="item_d_attribute_format"><code>d_attribute_format</code></a></strong>

<dd>
<p>From <em>d_attribut_format.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HASATTRIBUTE_FORMAT</code>, which
indicates the C compiler can check for printf-like formats.</p>
</dd>
</li>
<dt><strong><a name="item_d_attribute_malloc"><code>d_attribute_malloc</code></a></strong>

<dd>
<p>From <em>d_attribute_malloc.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HASATTRIBUTE_MALLOC</code>, which
indicates the C compiler can understand functions as having
malloc-like semantics.</p>
</dd>
</li>
<dt><strong><a name="item_d_attribute_nonnull"><code>d_attribute_nonnull</code></a></strong>

<dd>
<p>From <em>d_attribute_nonnull.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HASATTRIBUTE_NONNULL</code>, which
indicates that the C compiler can know that certain arguments
must not be <code>NULL</code>, and will check accordingly at compile time.</p>
</dd>
</li>
<dt><strong><a name="item_d_attribute_noreturn"><code>d_attribute_noreturn</code></a></strong>

<dd>
<p>From <em>d_attribute_noreturn.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HASATTRIBUTE_NORETURN</code>, which
indicates that the C compiler can know that certain functions
are guaranteed never to return.</p>
</dd>
</li>
<dt><strong><a name="item_d_attribute_pure"><code>d_attribute_pure</code></a></strong>

<dd>
<p>From <em>d_attribute_pure.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HASATTRIBUTE_PURE</code>, which
indicates that the C compiler can know that certain functions
are <code>pure</code> functions, meaning that they have no side effects, and
only rely on function input <em>and/or</em> global data for their results.</p>
</dd>
</li>
<dt><strong><a name="item_d_attribute_unused"><code>d_attribute_unused</code></a></strong>

<dd>
<p>From <em>d_attribute_unused.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines <code>HASATTRIBUTE_UNUSED</code>, which
indicates that the C compiler can know that certain variables
and arguments may not always be used, and to not throw warnings
if they don't get used.</p>
</dd>
</li>
<dt><strong><a name="item_d_attribute_warn_unused_result"><code>d_attribute_warn_unused_result</code></a></strong>

<dd>
<p>From <em>d_attribute_warn_unused_result.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines
<code>HASATTRIBUTE_WARN_UNUSED_RESULT</code>, which indicates that the C
compiler can know that certain functions have a return values
that must not be ignored, such as <code>malloc()</code> or open().</p>
</dd>
</li>
<dt><strong><a name="item_d_bcmp"><code>d_bcmp</code></a></strong>

<dd>
<p>From <em>d_bcmp.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_BCMP</code> symbol if
the <code>bcmp()</code> routine is available to compare strings.</p>
</dd>
</li>
<dt><strong><a name="item_d_bcopy"><code>d_bcopy</code></a></strong>

<dd>
<p>From <em>d_bcopy.U</em>:</p>
</dd>
<dd>
<p>This variable conditionally defines the <code>HAS_BCOPY</code> symbol if
the <code>bcopy()</code> routine is available to copy strings.</p>
</dd>
</li>
<dt><strong><a name="item_d_bsd"><code>d_bsd</code></a></strong>

<dd>
<p>From <em>Guess.U</em>:</p>
</dd>
<dd>
<p>This symbol conditionally defines the symbol <code>BSD</code> when running on a
<code>BSD</code> system.</p>
</dd>
</li>
<dt><strong><a name="item_d_bsdgetpgrp"><code>d_bsdgetpgrp</code></a></strong>

<dd>
<p>From <em>d_getpgrp.U</em>:</p>
</dd>
<dd>