SYSCONF(2P)SYSCONF(2P)NAMEsysconf - (POSIX only) get configurable system variables
SYNOPSIS
#include <unistd.h>
long sysconf(int name);
DESCRIPTION
The information in this specification applies only to POSIX
applications.
The sysconf function provides a method for an application to determined
the current value of a configurable system limit or option.
The name argument represents the system variable to be queried. The
following variables are supported:
Variable name Value
{ARG_MAX} {_SC_ARG_MAX}
{CHILD_MAX} {_SC_CHILD_MAX}
{clock ticks/second} {_SC_CLK_TCK}
{NGROUPS_MAX} {_SC_NGROUPS_MAX}
{OPEN_MAX} {_SC_OPEN_MAX}
{STREAM_BUF} {_SC_STREAM_BUF}
{TZNAME_MAX} {_SC_TZNAME_MAX}
{_POSIX_JOB_CONTROL} {_SC_JOB_CONTROL}
{_POSIX_SAVED_IDS} {_SC_SAVED_IDS}
{_POSIX_VERSION} {_SC_VERSION}
The meaning of each variable is as follows:
Variable Description
{ARG_MAX} Maximum length of all
arguments + environment
strings to exec().
{CHILD_MAX} Maximum number of
simultaneous processes per
real user ID.
{clock ticks/second} The number of clock ticks per
second.
{NGROUPS_MAX} Maximum number of
simultaneous supplementary
group IDs per process.
{OPEN_MAX} Maximum number of
simultaneous open files per
process.
{STREAM_BUF} The number of streams that
one process can have open at
one time.
{TZNAME_MAX} The maximum number of bytes
supported for the name of a
time zone.
{_POSIX_JOB_CONTROL} If defined, the system
supports POSIX job control.
{_POSIX_SAVED_IDS} If defined, saved set-user-
IDs and set-group-IDS are
supported.
{_POSIX_VERSION} The version of POSIX
supported by the system.
The values for the variables above are given in the headers <limits.h>
or <unistd.h>. The symbolic constants used as values for name are
given in <unistd.h>.
RETURN VALUE
Upon successful completion sysconf returns the current variable value
on the system. If name is an invalid value, sysconf returns -1. If
the variable corresponding to name is associated with functionality
that is not supported by the system, sysconf shall return -1 without
changing the value of errno.
ERRORS
If any of the following conditions occur, sysconf returns -1 and set
errno to the corresponding value:
[EINVAL] The value of name is invalid.
August 1, 1992 SYSCONF(2P)
