limits.h.html

IEEE 1003.1-2003, Single Unix Specification v3

<dt>{_POSIX_NGROUPS_MAX}</dt>

<dd>
Maximum number of simultaneous supplementary group IDs per process.<br>
Value: 8</dd>

<dt>{_POSIX_OPEN_MAX}</dt>

<dd>
Maximum number of files that one process can have open at any one time.<br>
Value: 20</dd>

<dt>{_POSIX_PATH_MAX}</dt>

<dd>
Maximum number of bytes in a pathname.<br>
Value: 256</dd>

<dt>{_POSIX_PIPE_BUF}</dt>

<dd>
Maximum number of bytes that is guaranteed to be atomic when writing to a pipe.<br>
Value: 512</dd>

<dt>{_POSIX_RE_DUP_MAX}</dt>

<dd>
The number of repeated occurrences of a BRE permitted by the <a href="../functions/regexec.html"><i>regexec</i>()</a> and <a href=
"../functions/regcomp.html"><i>regcomp</i>()</a> functions when using the interval notation {\(<i>m</i>,<i>n</i>\}; see <a href=
"xbd_chap09.html#tag_09_03_06"><i>BREs Matching Multiple Characters</i></a> .<br>
Value: 255</dd>

<dt>{_POSIX_RTSIG_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('RTS')">RTS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of realtime signal numbers reserved for application use.<br>
Value: 8 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_SEM_NSEMS_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('SEM')">SEM</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of semaphores that a process may have.<br>
Value: 256 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_SEM_VALUE_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('SEM')">SEM</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The maximum value a semaphore may have.<br>
Value: 32 767 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_SIGQUEUE_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('RTS')">RTS</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of queued signals that a process may send and have pending at the receiver(s) at any time.<br>
Value: 32 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_SSIZE_MAX}</dt>

<dd>
The value that can be stored in an object of type <b>ssize_t</b>.<br>
Value: 32 767</dd>

<dt>{_POSIX_STREAM_MAX}</dt>

<dd>
The number of streams that one process can have open at one time.<br>
Value: 8</dd>

<dt>{_POSIX_SS_REPL_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('SS')">SS|TSP</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of replenishment operations that may be simultaneously pending for a particular sporadic server scheduler.<br>
Value: 4 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_SYMLINK_MAX}</dt>

<dd>
The number of bytes in a symbolic link.<br>
Value: 255</dd>

<dt>{_POSIX_SYMLOOP_MAX}</dt>

<dd>
The number of symbolic links that can be traversed in the resolution of a pathname in the absence of a loop.<br>
Value: 8</dd>

<dt>{_POSIX_THREAD_DESTRUCTOR_ITERATIONS}</dt>

<dd><sup>[<a href="javascript:open_code('THR')">THR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of attempts made to destroy a thread's thread-specific data values on thread exit.<br>
Value: 4 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_THREAD_KEYS_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('THR')">THR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of data keys per process.<br>
Value: 128 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_THREAD_THREADS_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('THR')">THR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of threads per process.<br>
Value: 64 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_TIMER_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('TMR')">TMR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The per-process number of timers.<br>
Value: 32 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_TRACE_EVENT_NAME_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('TRC')">TRC</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The length in bytes of a trace event name.<br>
Value: 30 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_TRACE_NAME_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('TRC')">TRC</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The length in bytes of a trace generation version string or a trace stream name.<br>
Value: 8 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_TRACE_SYS_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('TRC')">TRC</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of trace streams that may simultaneously exist in the system.<br>
Value: 8 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_TRACE_USER_EVENT_MAX}</dt>

<dd><sup>[<a href="javascript:open_code('TRC')">TRC</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border=
"0"><br>
The number of user trace event type identifiers that may simultaneously exist in a traced process, including the predefined user
trace event POSIX_TRACE_UNNAMED_USER_EVENT.<br>
Value: 32 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_POSIX_TTY_NAME_MAX}</dt>

<dd>
The size of the storage required for a terminal device name, in bytes, including the terminating null.<br>
Value: 9</dd>

<dt>{_POSIX_TZNAME_MAX}</dt>

<dd>
Maximum number of bytes supported for the name of a timezone (not of the <i>TZ</i> variable).<br>
Value: 6 <basefont size="2"> 

<dl>
<dt><b>Note:</b></dt>

<dd>The length given by {_POSIX_TZNAME_MAX} does not include the quoting characters mentioned in <a href=
"xbd_chap08.html#tag_08_03"><i>Other Environment Variables</i></a> .</dd>
</dl>

<basefont size="3"></dd>

<dt>{_POSIX2_BC_BASE_MAX}</dt>

<dd>
Maximum <i>obase</i> values allowed by the <a href="../utilities/bc.html"><i>bc</i></a> utility.<br>
Value: 99</dd>

<dt>{_POSIX2_BC_DIM_MAX}</dt>

<dd>
Maximum number of elements permitted in an array by the <a href="../utilities/bc.html"><i>bc</i></a> utility.<br>
Value: 2 048</dd>

<dt>{_POSIX2_BC_SCALE_MAX}</dt>

<dd>
Maximum <i>scale</i> value allowed by the <a href="../utilities/bc.html"><i>bc</i></a> utility.<br>
Value: 99</dd>

<dt>{_POSIX2_BC_STRING_MAX}</dt>

<dd>
Maximum length of a string constant accepted by the <a href="../utilities/bc.html"><i>bc</i></a> utility.<br>
Value: 1 000</dd>

<dt>{_POSIX2_CHARCLASS_NAME_MAX}</dt>

<dd>
Maximum number of bytes in a character class name.<br>
Value: 14</dd>

<dt>{_POSIX2_COLL_WEIGHTS_MAX}</dt>

<dd>
Maximum number of weights that can be assigned to an entry of the <i>LC_COLLATE</i> <b>order</b> keyword in the locale definition
file; see <a href="xbd_chap07.html#tag_07"><i>Locale</i></a> .<br>
Value: 2</dd>

<dt>{_POSIX2_EXPR_NEST_MAX}</dt>

<dd>
Maximum number of expressions that can be nested within parentheses by the <a href="../utilities/expr.html"><i>expr</i></a>
utility.<br>
Value: 32</dd>

<dt>{_POSIX2_LINE_MAX}</dt>

<dd>
Unless otherwise noted, the maximum length, in bytes, of a utility's input line (either standard input or another file), when the
utility is described as processing text files. The length includes room for the trailing &lt;newline&gt;.<br>
Value: 2 048</dd>

<dt>{_POSIX2_RE_DUP_MAX]</dt>

<dd>
Maximum number of repeated occurrences of a regular expression permitted when using the interval notation \{<i>m</i>,<i>n</i>\};
see <a href="xbd_chap09.html#tag_09"><i>Regular Expressions</i></a> .<br>
Value: 255</dd>

<dt>{_XOPEN_IOV_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 <b>iovec</b> structures that one process has available for use with <a href=
"../functions/readv.html"><i>readv</i>()</a> or <a href="../functions/writev.html"><i>writev</i>()</a>.<br>
Value: 16 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_XOPEN_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 filename (not including the terminating null).<br>
Value: 255 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{_XOPEN_PATH_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 pathname.<br>
Value: 1024 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
</dl>

<h5><a name="tag_13_24_03_06"></a>Numerical Limits</h5>

<p>The values in the following lists shall be defined in <i>&lt;limits.h&gt;</i> and are constant expressions suitable for use in
<b>#if</b> preprocessing directives. Moreover, except for {CHAR_BIT}, <sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup>
<img src="../images/opt-start.gif" alt="[Option Start]" border="0"> {DBL_DIG}, {DBL_MAX}, {FLT_DIG}, {FLT_MAX}, {LONG_BIT},
{WORD_BIT}, <img src="../images/opt-end.gif" alt="[Option End]" border="0"> and {MB_LEN_MAX}, the symbolic names are defined as
expressions of the correct type.</p>

<p>If the value of an object of type <b>char</b> is treated as a signed integer when used in an expression, the value of {CHAR_MIN}
is the same as that of {SCHAR_MIN} and the value of {CHAR_MAX} is the same as that of {SCHAR_MAX}. Otherwise, the value of
{CHAR_MIN} is 0 and the value of {CHAR_MAX} is the same as that of {UCHAR_MAX}.</p>

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

<dd>
Number of bits in a type <b>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:
8 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{CHAR_MAX}</dt>

<dd>
Maximum value of type <b>char</b>.<br>
Value: {UCHAR_MAX} or {SCHAR_MAX}</dd>

<dt>{CHAR_MIN}</dt>

<dd>
Minimum value of type <b>char</b>.<br>
Value: {SCHAR_MIN} or 0</dd>

<dt>{INT_MAX}</dt>

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

<dt>{LONG_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 <b>long</b>.<br>
Minimum Acceptable Value: 32 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>

<dt>{LONG_MAX}</dt>

<dd>
Maximum value of a <b>long</b>.<br>
Minimum Acceptable Value: [phone]</dd>

<dt>{MB_LEN_MAX}</dt>

<dd>
Maximum number of bytes in a character, for any supported locale.<br>
Minimum Acceptable Value: 1</dd>

<dt>{SCHAR_MAX}</dt>

<dd>
Maximum 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: