limits.h.html

IEEE 1003.1-2003, Single Unix Specification v3

+127 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{SHRT_MAX}</dt>

<dd>
Maximum value of type <b>short</b>.<br>
Minimum Acceptable Value: +32 767</dd>

<dt>{SSIZE_MAX}</dt>

<dd>
Maximum value of an object of type <b>ssize_t</b>.<br>
Minimum Acceptable Value: {_POSIX_SSIZE_MAX}</dd>

<dt>{UCHAR_MAX}</dt>

<dd>
Maximum value of type <b>unsigned char</b>.<br>
<sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> Value:
255 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{UINT_MAX}</dt>

<dd>
Maximum value of type <b>unsigned</b>.<br>
Minimum Acceptable Value: 4 294 967 295</dd>

<dt>{ULONG_MAX}</dt>

<dd>
Maximum value of type <b>unsigned long</b>.<br>
Minimum Acceptable Value: 4 294 967 295</dd>

<dt>{USHRT_MAX}</dt>

<dd>
Maximum value for a type <b>unsigned short</b>.<br>
Minimum Acceptable Value: 65 535</dd>

<dt>{WORD_BIT}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Number of bits in a word or type <b>int</b>.<br>
Minimum Acceptable Value: 16 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{INT_MIN}</dt>

<dd>
Minimum value of type <b>int</b>.<br>
Maximum Acceptable Value: -2 147 483 647</dd>

<dt>{LONG_MIN}</dt>

<dd>
Minimum value of type <b>long</b>.<br>
Maximum Acceptable Value: -2 147 483 647</dd>

<dt>{SCHAR_MIN}</dt>

<dd>
Minimum value of type <b>signed char</b>.<br>
<sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> Value:
-128 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{SHRT_MIN}</dt>

<dd>
Minimum value of type <b>short</b>.<br>
Maximum Acceptable Value: -32 767</dd>

<dt>{LLONG_MIN}</dt>

<dd>
Minimum value of type <b>long long</b>.<br>
Maximum Acceptable Value: -9223372036854775807</dd>

<dt>{LLONG_MAX}</dt>

<dd>
Maximum value of type <b>long long</b>.<br>
Minimum Acceptable Value: +9223372036854775807</dd>

<dt>{ULLONG_MAX}</dt>

<dd>
Maximum value of type <b>unsigned long long</b>.<br>
Minimum Acceptable Value: 18446744073709551615</dd>
</dl>

<h5><a name="tag_13_24_03_07"></a>Other Invariant Values</h5>

<p><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
The following constants shall be defined on all implementations in <i>&lt;limits.h&gt;</i>: <img src="../images/opt-end.gif" alt=
"[Option End]" border="0"></p>

<dl compact>
<dt>{CHARCLASS_NAME_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Maximum number of bytes in a character class name.<br>
Minimum Acceptable Value: 14 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{NL_ARGMAX}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Maximum value of <i>digit</i> in calls to the <a href="../functions/printf.html"><i>printf</i>()</a> and <a href=
"../functions/scanf.html"><i>scanf</i>()</a> functions.<br>
Minimum Acceptable Value: 9 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{NL_LANGMAX}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Maximum number of bytes in a <i>LANG</i> name.<br>
Minimum Acceptable Value: 14 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{NL_MSGMAX}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Maximum message number.<br>
Minimum Acceptable Value: 32 767 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{NL_NMAX}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Maximum number of bytes in an N-to-1 collation mapping.<br>
Minimum Acceptable Value: No guaranteed value across all conforming implementations. <img src="../images/opt-end.gif" alt=
"[Option End]" border="0"></dd>

<dt>{NL_SETMAX}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Maximum set number.<br>
Minimum Acceptable Value: 255 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{NL_TEXTMAX}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Maximum number of bytes in a message string.<br>
Minimum Acceptable Value: {_POSIX2_LINE_MAX} <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{NZERO}</dt>

<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
Default process priority.<br>
Minimum Acceptable Value: 20 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
</dl>
</blockquote>

<hr>
<div class="box"><em>The following sections are informative.</em></div>

<h4><a name="tag_13_24_04"></a>APPLICATION USAGE</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_13_24_05"></a>RATIONALE</h4>

<blockquote>
<p>A request was made to reduce the value of {_POSIX_LINK_MAX} from the value of 8 specified for it in the POSIX.1-1990 standard to
2. The standard developers decided to deny this request for several reasons:</p>

<ul>
<li>
<p>They wanted to avoid making any changes to the standard that could break conforming applications, and the requested change could
have that effect.</p>
</li>

<li>
<p>The use of multiple hard links to a file cannot always be replaced with use of symbolic links. Symbolic links are semantically
different from hard links in that they associate a pathname with another pathname rather than a pathname with a file. This has
implications for access control, file permanence, and transparency.</p>
</li>

<li>
<p>The original standard developers had considered the issue of allowing for implementations that did not in general support hard
links, and decided that this would reduce consensus on the standard.</p>
</li>
</ul>

<p>Systems that support historical versions of the development option of the ISO&nbsp;POSIX-2 standard retain the name
{_POSIX2_RE_DUP_MAX} as an alias for {_POSIX_RE_DUP_MAX}.</p>

<dl compact>
<dt>{PATH_MAX}</dt>

<dd>
IEEE PASC Interpretation 1003.1 #15 addressed the inconsistency in the standard with the definition of pathname and the description
of {PATH_MAX}, allowing application writers to allocate either {PATH_MAX} or {PATH_MAX}+1 bytes. The inconsistency has been removed
by correction to the {PATH_MAX} definition to include the null character. With this change, applications that previously allocated
{PATH_MAX} bytes will continue to succeed.</dd>

<dt>{SYMLINK_MAX}</dt>

<dd>
This symbol refers to space for data that is stored in the file system, as opposed to {PATH_MAX} which is the length of a name that
can be passed to a function. In some existing implementations, the filenames pointed to by symbolic links are stored in the inodes
of the links, so it is important that {SYMLINK_MAX} not be constrained to be as large as {PATH_MAX}.</dd>
</dl>
</blockquote>

<h4><a name="tag_13_24_06"></a>FUTURE DIRECTIONS</h4>

<blockquote>
<p>None.</p>
</blockquote>

<h4><a name="tag_13_24_07"></a>SEE ALSO</h4>

<blockquote>
<p>The System Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href="../functions/fpathconf.html"><i>fpathconf</i>()</a>, <a
href="../functions/pathconf.html"><i>pathconf</i>()</a>, <a href="../functions/sysconf.html"><i>sysconf</i>()</a></p>
</blockquote>

<h4><a name="tag_13_24_08"></a>CHANGE HISTORY</h4>

<blockquote>
<p>First released in Issue 1.</p>
</blockquote>

<h4><a name="tag_13_24_09"></a>Issue 5</h4>

<blockquote>
<p>The DESCRIPTION is updated for alignment with the POSIX Realtime Extension and the POSIX Threads Extension.</p>

<p>{FILESIZEBITS} is added for the Large File Summit extensions.</p>

<p>The minimum acceptable values for {INT_MAX}, {INT_MIN}, and {UINT_MAX} are changed to make 32-bit values the minimum
requirement.</p>

<p>The entry is restructured to improve readability.</p>
</blockquote>

<h4><a name="tag_13_24_10"></a>Issue 6</h4>

<blockquote>
<p>The Open Group Corrigendum U033/4 is applied. The wording is made clear for {CHAR_MIN}, {INT_MIN}, {LONG_MIN}, {SCHAR_MIN}, and
{SHRT_MIN} that these are maximum acceptable values.</p>

<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>

<ul>
<li>
<p>The minimum value for {CHILD_MAX} is 25. This is a FIPS requirement.</p>
</li>

<li>
<p>The minimum value for {OPEN_MAX} is 20. This is a FIPS requirement.</p>
</li>

<li>
<p>The minimum value for {NGROUPS_MAX} is 8. This is also a FIPS requirement.</p>
</li>
</ul>

<p>Symbolic constants are added for {_POSIX_SYMLINK_MAX}, {_POSIX_SYMLOOP_MAX}, {_POSIX_RE_DUP_MAX}, {RE_DUP_MAX}, {SYMLOOP_MAX},
and {SYMLINK_MAX}.</p>

<p>The following values are added for alignment with IEEE&nbsp;Std&nbsp;1003.1d-1999: {_POSIX_SS_REPL_MAX} {SS_REPL_MAX}
{POSIX_ALLOC_SIZE_MIN} {POSIX_REC_INCR_XFER_SIZE} {POSIX_REC_MAX_XFER_SIZE} {POSIX_REC_MIN_XFER_SIZE} {POSIX_REC_XFER_ALIGN}</p>

<p>Reference to CLOCK_MONOTONIC is added in the description of {_POSIX_CLOCKRES_MIN} for alignment with
IEEE&nbsp;Std&nbsp;1003.1j-2000.</p>

<p>The constants {LLONG_MIN}, {LLONG_MAX}, and {ULLONG_MAX} are added for alignment with the ISO/IEC&nbsp;9899:1999 standard.</p>

<p>The following values are added for alignment with IEEE&nbsp;Std&nbsp;1003.1q-2000: {_POSIX_TRACE_EVENT_NAME_MAX}
{_POSIX_TRACE_NAME_MAX} {_POSIX_TRACE_SYS_MAX} {_POSIX_TRACE_USER_EVENT_MAX} {TRACE_EVENT_NAME_MAX} {TRACE_NAME_MAX}
{TRACE_SYS_MAX} {TRACE_USER_EVENT_MAX}</p>

<p>The new limits {_XOPEN_NAME_MAX} and {_XOPEN_PATH_MAX} are added as minimum values for {PATH_MAX} and {NAME_MAX} limits on
XSI-conformant systems.</p>

<p>The legacy symbols {PASS_MAX} and {TMP_MAX} are removed.</p>

<p>The values for the limits {CHAR_BIT}, {SCHAR_MAX}, and {UCHAR_MAX} are now required to be 8, +127, and 255, respectively.</p>

<p>The value for the limit {CHAR_MAX} is now {UCHAR_MAX} or {SCHAR_MAX}.</p>

<p>The value for the limit {CHAR_MIN} is now {SCHAR_MIN} or zero.</p>

<p>IEEE&nbsp;Std 1003.1-2001/Cor&nbsp;1-2002, item XBD/TC1/D6/10 is applied, updating the value of {_POSIX_CHILD_MAX} from 6 to 25.
This corrects an editorial error and is for FIPS 151-2 alignment.</p>
</blockquote>

<div class="box"><em>End of informative text.</em></div>

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