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 <h3 class="section">31.5 Minimum Values for General Capacity Limits</h3>

 <p>Here are the names for the POSIX minimum upper bounds for the system
 limit parameters.  The significance of these values is that you can
 safely push to these limits without checking whether the particular
 system you are using can go that far.

      <dl>
 <!-- limits.h -->
 <!-- POSIX.1 -->
 <dt><code>_POSIX_AIO_LISTIO_MAX</code><dd>The most restrictive limit permitted by POSIX for the maximum number of
 I/O operations that can be specified in a list I/O call.  The value of
 this constant is <code>2</code>; thus you can add up to two new entries
 of the list of outstanding operations.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_AIO_MAX</code><dd>The most restrictive limit permitted by POSIX for the maximum number of
 outstanding asynchronous I/O operations.  The value of this constant is
 <code>1</code>.  So you cannot expect that you can issue more than one
 operation and immediately continue with the normal work, receiving the
 notifications asynchronously.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_ARG_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the maximum combined length of the <var>argv</var> and <var>environ</var>
 arguments that can be passed to the <code>exec</code> functions.
 Its value is <code>4096</code>.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_CHILD_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the maximum number of simultaneous processes per real user ID.  Its
 value is <code>6</code>.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_NGROUPS_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the maximum number of supplementary group IDs per process.  Its
 value is <code>0</code>.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_OPEN_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the maximum number of files that a single process can have open
 simultaneously.  Its value is <code>16</code>.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_SSIZE_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the maximum value that can be stored in an object of type
 <code>ssize_t</code>.  Its value is <code>32767</code>.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_STREAM_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the maximum number of streams that a single process can have open
 simultaneously.  Its value is <code>8</code>.

      <!-- limits.h -->
      <!-- POSIX.1 -->
      <br><dt><code>_POSIX_TZNAME_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the maximum length of a time zone name.  Its value is <code>3</code>.

      <!-- limits.h -->
      <!-- POSIX.2 -->
      <br><dt><code>_POSIX2_RE_DUP_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
 for the numbers used in the &lsquo;<samp><span class="samp">\{</span><var>min</var><span class="samp">,</span><var>max</var><span class="samp">\}</span></samp>&rsquo; construct
 in a regular expression.  Its value is <code>255</code>.
 </dl>

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	This file documents the GNU C library.

	This is Edition 0.12, last updated 2007-10-27,
	of `The GNU C Library Reference Manual', for version
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	Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002,
	2003, 2007, 2008, 2010 Free Software Foundation, Inc.

	Permission is granted to copy, distribute and/or modify this document
	under the terms of the GNU Free Documentation License, Version 1.3 or
	any later version published by the Free Software Foundation; with the
	Invariant Sections being ``Free Software Needs Free Documentation''
	and ``GNU Lesser General Public License'', the Front-Cover texts being
	``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A
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	<h3 class="section">31.5 Minimum Values for General Capacity Limits</h3>

	<p>Here are the names for the POSIX minimum upper bounds for the system
	limit parameters. The significance of these values is that you can
	safely push to these limits without checking whether the particular
	system you are using can go that far.

	<dl>
	<!-- limits.h -->
	<!-- POSIX.1 -->
	<dt><code>_POSIX_AIO_LISTIO_MAX</code><dd>The most restrictive limit permitted by POSIX for the maximum number of
	I/O operations that can be specified in a list I/O call. The value of
	this constant is <code>2</code>; thus you can add up to two new entries
	of the list of outstanding operations.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_AIO_MAX</code><dd>The most restrictive limit permitted by POSIX for the maximum number of
	outstanding asynchronous I/O operations. The value of this constant is
	<code>1</code>. So you cannot expect that you can issue more than one
	operation and immediately continue with the normal work, receiving the
	notifications asynchronously.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_ARG_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the maximum combined length of the <var>argv</var> and <var>environ</var>
	arguments that can be passed to the <code>exec</code> functions.
	Its value is <code>4096</code>.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_CHILD_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the maximum number of simultaneous processes per real user ID. Its
	value is <code>6</code>.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_NGROUPS_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the maximum number of supplementary group IDs per process. Its
	value is <code>0</code>.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_OPEN_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the maximum number of files that a single process can have open
	simultaneously. Its value is <code>16</code>.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_SSIZE_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the maximum value that can be stored in an object of type
	<code>ssize_t</code>. Its value is <code>32767</code>.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_STREAM_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the maximum number of streams that a single process can have open
	simultaneously. Its value is <code>8</code>.

	<!-- limits.h -->
	<!-- POSIX.1 -->
	<br><dt><code>_POSIX_TZNAME_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the maximum length of a time zone name. Its value is <code>3</code>.

	<!-- limits.h -->
	<!-- POSIX.2 -->
	<br><dt><code>_POSIX2_RE_DUP_MAX</code><dd>The value of this macro is the most restrictive limit permitted by POSIX
	for the numbers used in the ‘<samp><span class="samp">\{</span><var>min</var><span class="samp">,</span><var>max</var><span class="samp">\}</span></samp>’ construct
	in a regular expression. Its value is <code>255</code>.
	</dl>

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