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SYSCONF(3)	       FreeBSD Library Functions Manual		    SYSCONF(3)

NAME
     sysconf --	get configurable system	variables

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <unistd.h>

     long
     sysconf(int name);

DESCRIPTION
     This interface is defined by IEEE Std 1003.1-1988 (``POSIX.1'').  A far
     more complete interface is	available using	sysctl(3).

     The sysconf() function provides a method for applications to determine
     the current value of a configurable system	limit or option	variable.  The
     name argument specifies the system	variable to be queried.	 Symbolic con-
     stants for	each name value	are found in the include file <unistd.h>.
     Shell programmers who need	access to these	parameters should use the
     getconf(1)	utility.

     The available values are as follows:

     _SC_ARG_MAX
	     The maximum bytes of argument to execve(2).

     _SC_CHILD_MAX
	     The maximum number	of simultaneous	processes per user id.

     _SC_CLK_TCK
	     The frequency of the statistics clock in ticks per	second.

     _SC_IOV_MAX
	     The maximum number	of elements in the I/O vector used by
	     readv(2), writev(2), recvmsg(2), and sendmsg(2).

     _SC_NGROUPS_MAX
	     The maximum number	of supplemental	groups.

     _SC_NPROCESSORS_CONF
	     The number	of processors configured.

     _SC_NPROCESSORS_ONLN
	     The number	of processors currently	online.

     _SC_OPEN_MAX
	     One more than the maximum value the system	may assign to a	new
	     file descriptor.

     _SC_PAGESIZE
	     The size of a system page in bytes.

     _SC_PAGE_SIZE
	     Equivalent	to _SC_PAGESIZE.

     _SC_STREAM_MAX
	     The minimum maximum number	of streams that	a process may have
	     open at any one time.

     _SC_TZNAME_MAX
	     The minimum maximum number	of types supported for the name	of a
	     timezone.

     _SC_JOB_CONTROL
	     Return 1 if job control is	available on this system, otherwise
	     -1.

     _SC_SAVED_IDS
	     Returns 1 if saved	set-group and saved set-user ID	is available,
	     otherwise -1.

     _SC_VERSION
	     The version of IEEE Std 1003.1 (``POSIX.1'') with which the sys-
	     tem attempts to comply.

     _SC_BC_BASE_MAX
	     The maximum ibase/obase values in the bc(1) utility.

     _SC_BC_DIM_MAX
	     The maximum array size in the bc(1) utility.

     _SC_BC_SCALE_MAX
	     The maximum scale value in	the bc(1) utility.

     _SC_BC_STRING_MAX
	     The maximum string	length in the bc(1) utility.

     _SC_COLL_WEIGHTS_MAX
	     The maximum number	of weights that	can be assigned	to any entry
	     of	the LC_COLLATE order keyword in	the locale definition file.

     _SC_EXPR_NEST_MAX
	     The maximum number	of expressions that can	be nested within
	     parenthesis by the	expr(1)	utility.

     _SC_LINE_MAX
	     The maximum length	in bytes of a text-processing utility's	input
	     line.

     _SC_RE_DUP_MAX
	     The maximum number	of repeated occurrences	of a regular expres-
	     sion permitted when using interval	notation.

     _SC_2_VERSION
	     The version of IEEE Std 1003.2 (``POSIX.2'') with which the sys-
	     tem attempts to comply.

     _SC_2_C_BIND
	     Return 1 if the system's C-language development facilities	sup-
	     port the C-Language Bindings Option, otherwise -1.

     _SC_2_C_DEV
	     Return 1 if the system supports the C-Language Development	Utili-
	     ties Option, otherwise -1.

     _SC_2_CHAR_TERM
	     Return 1 if the system supports at	least one terminal type	capa-
	     ble of all	operations described in	IEEE Std 1003.2	(``POSIX.2''),
	     otherwise -1.

     _SC_2_FORT_DEV
	     Return 1 if the system supports the FORTRAN Development Utilities
	     Option, otherwise -1.

     _SC_2_FORT_RUN
	     Return 1 if the system supports the FORTRAN Runtime Utilities
	     Option, otherwise -1.

     _SC_2_LOCALEDEF
	     Return 1 if the system supports the creation of locales, other-
	     wise -1.

     _SC_2_SW_DEV
	     Return 1 if the system supports the Software Development Utili-
	     ties Option, otherwise -1.

     _SC_2_UPE
	     Return 1 if the system supports the User Portability Utilities
	     Option, otherwise -1.

     _SC_AIO_LISTIO_MAX
	     Maximum number of I/O operations in a single list I/O call	sup-
	     ported.

     _SC_AIO_MAX
	     Maximum number of outstanding asynchronous	I/O operations sup-
	     ported.

     _SC_AIO_PRIO_DELTA_MAX
	     The maximum amount	by which a process can decrease	its asynchro-
	     nous I/O priority level from its own scheduling priority.

     _SC_DELAYTIMER_MAX
	     Maximum number of timer expiration	overruns.

     _SC_MQ_OPEN_MAX
	     The maximum number	of open	message	queue descriptors a process
	     may hold.

     _SC_RTSIG_MAX
	     Maximum number of realtime	signals	reserved for application use.

     _SC_SEM_NSEMS_MAX
	     Maximum number of semaphores that a process may have.

     _SC_SEM_VALUE_MAX
	     The maximum value a semaphore may have.

     _SC_SIGQUEUE_MAX
	     Maximum number of queued signals that a process may send and have
	     pending at	the receiver(s)	at any time.

     _SC_TIMER_MAX
	     Maximum number of timers per process supported.

     _SC_GETGR_R_SIZE_MAX
	     Suggested initial value for the size of the group entry buffer.

     _SC_GETPW_R_SIZE_MAX
	     Suggested initial value for the size of the password entry
	     buffer.

     _SC_HOST_NAME_MAX
	     Maximum length of a host name (not	including the terminating
	     null) as returned from the	gethostname() function.

     _SC_LOGIN_NAME_MAX
	     Maximum length of a login name.

     _SC_THREAD_STACK_MIN
	     Minimum size in bytes of thread stack storage.

     _SC_THREAD_THREADS_MAX
	     Maximum number of threads that can	be created per process.

     _SC_TTY_NAME_MAX
	     Maximum length of terminal	device name.

     _SC_SYMLOOP_MAX
	     Maximum number of symbolic	links that can be reliably traversed
	     in	the resolution of a pathname in	the absence of a loop.

     _SC_ATEXIT_MAX
	     Maximum number of functions that may be registered	with atexit().

     _SC_XOPEN_VERSION
	     An	integer	value greater than or equal to 4, indicating the ver-
	     sion of the X/Open	Portability Guide to which this	system con-
	     forms.

     _SC_XOPEN_XCU_VERSION
	     An	integer	value indicating the version of	the XCU	Specification
	     to	which this system conforms.

     These values also exist, but may not be standard:

     _SC_CPUSET_SIZE
	     Size of the kernel	cpuset.

     _SC_PHYS_PAGES
	     The number	of pages of physical memory.  Note that	it is possible
	     that the product of this value and	the value of _SC_PAGESIZE will
	     overflow a	long in	some configurations on a 32bit machine.

RETURN VALUES
     If	the call to sysconf() is not successful, -1 is returned	and errno is
     set appropriately.	 Otherwise, if the variable is associated with func-
     tionality that is not supported, -1 is returned and errno is not modi-
     fied.  Otherwise, the current variable value is returned.

ERRORS
     The sysconf() function may	fail and set errno for any of the errors spec-
     ified for the library function sysctl(3).	In addition, the following
     error may be reported:

     [EINVAL]		The value of the name argument is invalid.

SEE ALSO
     getconf(1), pathconf(2), confstr(3), sysctl(3)

STANDARDS
     Except for	the fact that values returned by sysconf() may change over the
     lifetime of the calling process, this function conforms to	IEEE Std
     1003.1-1988 (``POSIX.1'').

HISTORY
     The sysconf() function first appeared in 4.4BSD.

BUGS
     The value for _SC_STREAM_MAX is a minimum maximum,	and required to	be the
     same as ANSI C's FOPEN_MAX, so the	returned value is a ridiculously small
     and misleading number.

FreeBSD	9.2			April 26, 2013			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY | BUGS

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