#include <unistd.h>
long sysconf (name)
int name ;
Description
The
sysconf
function provides a method for the application to determine the
current value of a configurable system limit or option (
variable).
The name argument represents the system variable to be queried.
In the table that follows, the values in the left column are
defined in <limits.h>, except for CLK_TCK,
which is defined in <time.h>. The values in the
right column are defined in <unistd.h>. The information in the
right column comprise the possible values for the name
argument.
Variable
name Value
{ARG_MAX}
{_SC_ARG_MAX}
{CHILD_MAX}
{_SC_CHILD_MAX}
{CLK_TCK}
{_SC_CLK_TCK}
{NGROUPS_MAX}
{_SC_NGROUPS_MAX}
{OPEN_MAX}
{_SC_OPEN_MAX}
{PASS_MAX}
{_SC_PASS_MAX}
{_POSIX_JOB_CONTROL}
{_SC_JOB_CONTROL}
{_POSIX_SAVED_IDS}
{_SC_SAVED_IDS}
{_POSIX_VERSION}
{_SC_VERSION}
The value returned by sysconf for _SC_CLK_TCK
is the same as CLK_TCK.
Return value
If name is an invalid value, sysconf
returns a -1. If the variable corresponding to name
is not defined on the system, sysconf
returns -1 without changing the value of errno.
Otherwise, sysconf
returns the current variable value on
the system. The value returned is not more restrictive than the
corresponding value described to the application when it was compiled
with the implementation's
<time.h>
or
<unistd.h>.
The value does not change during the lifetime of the calling process.
Diagnostics
If any of the following conditions occur, the
sysconf
function returns -1 and sets
errno
to the corresponding value:
[EINVAL]
The value of the name argument is invalid.
Notes
PASS_MAX and _SC_PASS_MAX are
XPG3 extensions over POSIX.
Standards conformance
sysconf is conformant with:
IEEE POSIX Std 1003.1-1990 System Application Program Interface (API) [C Language] (ISO/IEC 9945-1)
;
and
NIST FIPS 151-1
.