Language Ccpp Cref Man Sysconf.htm

 <TITLE>sysconf</TITLE>
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<h3>SYSCONF(3) Linux Programmer's Manual SYSCONF(3)
</h3>
<h3>NAME
</h3> sysconf - Get configuration information at runtime
<h3>SYNOPSIS
</h3> #include &lt;unistd.h&gt;
 long sysconf(int name);
<h3>DESCRIPTION
</h3> sysconf() provides a way for the application to determine
 values for system limits or options at runtime.
 The equivalent macros defined in &lt;unistd.h&gt; can only give
 conservative values; if an application wants to take
 advantage of values which may change, a call to sysconf()
 can be made, which may yield more liberal results.
 For getting information about a particular file, see
 fpathconf() or pathconf().
 The following values are supported for name. First, the
 POSIX.1 compatible values:
 _SC_ARG_MAX
 The maximum length of the arguments to the exec()
 family of functions; the corresponding macro is
 ARG_MAX.
 _SC_CHILD_MAX
 The number of simultaneous processes per user id,
 the corresponding macro is _POSIX_CHILD_MAX.
 _SC_CLK_TCK
 The number of clock ticks per second; the corre-
 sponding macro is CLK_TCK.
 _SC_STREAM_MAX
 The maximum number of streams that a process can
 have open at any time. The corresponding POSIX
 macro is STREAM_MAX, the corresponding standard C
 macro is FOPEN_MAX.
 _SC_TZNAME_MAX
 The maximum number of bytes in a timezone name, the
 corresponding macro is TZNAME_MAX.
 _SC_OPEN_MAX
 The maximum number of files that a process can have
 open at any time, the corresponding macro is
 _POSIX_OPEN_MAX.
 _SC_JOB_CONTROL
 This indicates whether POSIX - style job control is
 supported, the corresponding macro is
<h3>GNU April 18, 1993 1
</h3>
<h3>SYSCONF(3) Linux Programmer's Manual SYSCONF(3)
</h3>
 _POSIX_JOB_CONTROL.
 _SC_SAVED_IDS
 This indicates whether a process has a saved set-
 user-ID and a saved set-group-ID; the corresponding
 macro is _POSIX_SAVED_IDS.
 _SC_VERSION
 indicates the year and month the POSIX.1 standard
 was approved in the format YYYYMML;the value
 199009L indicates the most recent revision, 1990.
 Next, the POSIX.2 values:
 _SC_BC_BASE_MAX
 indicates the maximum obase value accepted by the
 bc(1) utility; the corresponding macro is
 BC_BASE_MAX.
 _SC_BC_DIM_MAX
 indicates the maximum value of elements permitted
 in an array by bc(1); the corresponding macro is
 BC_DIM_MAX.
 _SC_BC_SCALE_MAX
 indicates the maximum scale value allowed by bc(1);
 the corresponding macro is BC_SCALE_MAX.
 _SC_BC_STRING_MAX
 indicates the maximum length of a string accepted
 by bc(1); the corresponding macro is BC_STRING_MAX.
 _SC_COLL_WEIGHTS_MAX
 indicates the maximum numbers of weights that can
 be assigned to an entry of the LC_COLLATE order
 keyword in the locale definition file; the corre-
 sponding macro is COLL_WEIGHTS_MAX.
 _SC_EXPR_NEST_MAX
 is the maximum number of expressions which can be
 nested within parentheses by expr(1). The corre-
 sponding macro is EXPR_NEST_MAX.
 _SC_LINE_MAX
 The maximum length of a utility's input line
 length, either from standard input or from a file.
 This includes length for a trailing newline. The
 corresponding macro is LINE_MAX.
 _SC_RE_DUP_MAX
 The maximum number of repeated occurrences of a
 regular expression when the interval notation
 \{m,n\} is used. The value of the corresponding
 macro is RE_DUP_MAX.
<h3>GNU April 18, 1993 2
</h3>
<h3>SYSCONF(3) Linux Programmer's Manual SYSCONF(3)
</h3>
 _SC_2_VERSION
 indicates the version of the POSIX.2 standard in
 the format of YYYYMML. The corresponding macro is
 POSIX2_VERSION.
 _SC_2_DEV
 indicates whether the POSIX.2 C language develop-
 ment facilities are supported. The corresponding
 macro is POSIX2_C_DEV.
 _SC_2_FORT_DEV
 indicates whether the POSIX.2 FORTRAN development
 utilities are supported. The corresponding macro
 is POSIX2_FORT_RUN.
 _SC_2_FORT_RUN
 indicates whether the POSIX.2 FORTRAN runtime util-
 ities are supported. The corresponding macro is
 POSIX2_FORT_RUN.
 POSIX2_LOCALEDEF
 indicates whether the POSIX.2 creation of locates
 via locale(1) is supported. The corresponding
 macro is POSIX2_LOCALEDEF.
 _SC_2_SW_DEV
 indicates whether the POSIX.2 software development
 utilities option is supported. The corresponding
 macro is POSIX2_SW_DEV.
<h3>RETURN VALUE
</h3> The value returned is the value of the system resource, 1
 if a queried option is available, 0 if it is not, or -1 on
 error. The variable errno is not set.
<h3>CONFORMS TO
</h3> POSIX.1, proposed POSIX.2
<h3>BUGS
</h3> It is difficult use ARG_MAX because it is not specified
 how much of the argument space for exec() is consumed by
 the user's environment variables.
 Some returned values may be huge; they are not suitable
 for allocating memory.
 POSIX.2 is not yet an approved standard; the information
 in this manpage is subject to change.
</pre>
<hr>
<h3>SEE ALSO
</h3><p>
<a href=bc.htm>bc</a>, 
<a href=expr.htm>expr</a>, 
<a href=locale.htm>locale</a>, 
<a href=fpathconf.htm>fpathconf</a>, 
<a href=pathconf.htm>pathconf</a>, 
<pre>
<h3>GNU April 18, 1993 3
</h3>
</pre>
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