sysconf(3C) sysconf(3C)
NAME
sysconf - get configurable system variables
SYNOPSIS
#include <unistd.h>
long sysconf(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. The following table lists the minimal set of system
variables from limits.h and unistd.h that can be returned by
sysconf, and the symbolic constants, defined in unistd.h that
are the corresponding values used for name.
NAME RETURN VALUE (minimum)
_______________________________________________
_SC_ARG_MAX ARG_MAX
_SC_CHILD_MAX CHILD_MAX
_SC_CLK_TCK CLK_TCK
_SC_JOB_CONTROL _POSIX_JOB_CONTROL
_SC_LOGNAME_MAX LOGNAME_MAX
_SC_NGROUPS_MAX NGROUPS_MAX
_SC_OPEN_MAX OPEN_MAX
_SC_PAGESIZE PAGESIZE
_SC_PASS_MAX PASS_MAX
_SC_SAVED_IDS _POSIX_SAVED_IDS
_SC_VERSION _POSIX_VERSION
_SC_XOPEN_VERSION _XOPEN_VERSION
_SC_BC_BASE_MAX _POSIX2_BC_BASE_MAX
_SC_BD_DIM_MAX _POSIX2_BC_DIM_MAX
_SC_BC_SCALE_MAX _POSIX2_BC_SCALE_MAX
_SC_BC_STRING_MAX _POSIX2_BC_STRING_MAX
_SC_COLL_WEIGHTS_MAX _POSIX2_COLL_WEIGHTS_MAX
_SC_EXPR_NEST_MAX _POSIX2_EXPR_NEST_MAX
_SC_RE_DUP_MAX _RE_DUP_MAX
_SC_LINE_MAX _POSIX2_LINE_MAX
_SC_TZNAME_MAX TZNAME_MAX
_SC_LINE_MAX 1
_SC_XOPEN_CRYPT 1
The value of CLK_TCK may be variable and it should not be
assumed that CLK_TCK is a compile-time constant. The value of
CLK_TCK is the same as the value of sysconf(_SC_CLK_TCK).
Copyright 1994 Novell, Inc. Page 1
sysconf(3C) sysconf(3C)
sysconf can also return the following values:
NAME RETURN VALUE
___________________________________________________________
_SC_NPROCESSORS_CONF Number of configured processors
_SC_NPROCESSORS_ONLN Number of online processors
_SC_NPROCESSES Number of processes per real user id
_SC_STREAM_MAX Minimum number of open streams per
process
Errors
If name is an invalid value, sysconf will return -1 and set
errno to indicate the error. If sysconf fails due to a value
of name that is not defined on the system, the function will
return a value of -1 without changing the value of errno.
The following variables return 1, that is, the feature is
supported:
_SC_XOPEN_SHM
_SC_XOPEN_CRYPT
The following variables return -1 if the feature is not
supported.
_SC_2_C_DEV
_SC_2_C_BIND
_SC_2_C_VERSION
_SC_2_CHAR_TERM
_SC_2_FORT_DEV
_SC_2_FORT_RUN
_SC_2_SW_DEV
_SC_2_UPE
_SC_XOPEN_ENH_I18N
_SC_2_LOCALDEF
_SC_2_VERSION
REFERENCES
fpathconf(2), getrlimit(2)
NOTICES
A call to setrlimit [see getrlimit(2)] may cause the value of
OPEN_MAX to change.
Copyright 1994 Novell, Inc. Page 2