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Name

Synopsis

#include <unistd.h>

long sysconf(int name);

Availability

MT-Level

Description

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 on the SPARC, x86 and PowerPC platforms.

Name	Return Value	Meaning
_SC_ARG_MAX	ARG_MAX	Max size of argv[] plus envp[].
_SC_CHILD_MAX	CHILD_MAX	Max processes allowed to a UID .
_SC_CLK_TCK	CLK_TCK	Ticks per second (clock_t).
_SC_NGROUPS_MAX	NGROUPS_MAX	Max simultaneous groups
		to which one may belong.
_SC_OPEN_MAX	OPEN_MAX	Max open files per process.
_SC_PASS_MAX	PASS_MAX
_SC_PAGESIZE	PAGESIZE	System memory page size.
_SC_JOB_CONTROL	_POSIX_JOB_CONTROL	Job control supported?
_SC_SAVED_IDS	_POSIX_SAVED_IDS	Saved IDs (seteuid()) supported?
_SC_VERSION	_POSIX_VERSION	POSIX.1 version supported.
_SC_XOPEN_VERSION	_XOPEN_VERSION
_SC_LOGNAME_MAX	LOGNAME_MAX
_SC_NPROCESSORS_CONF		Number of processors configured.
_SC_NPROCESSORS_ONLN		Number of processors online.
_SC_PHYS_PAGES		Total number of pages of
		physical memory in system.
_SC_AVPHYS_PAGES		Number physical memory pages
		not currently in use by system.
_SC_AIO_LISTIO_MAX	AIO_LISTIO_MAX	Max number of I/O operations
		in a single list I/O call
		supported by implementation.
_SC_AIO_MAX	AIO_MAX	Max number of outstanding
		asynchronous I/O operations
		supported by implementation.
_SC_AIO_PRIO_DELTA_MAX	AIO_PRIO_DELTA_MAX	Max amount by which a process
		can decrease its asynchronous
		/O priority level from its own
		scheduling priority.
_SC_DELAYTIMER_MAX	DELAYTIMER_MAX	Max number of timer
		expiration overruns.
_SC_GETGR_R_SIZE_MAX	NSS_BUFLEN_GROUP	Max size of group entry buffer.
_SC_GETPW_R_SIZE_MAX	NSS_BUFLEN_PASSWD	Max size of password entry buffer.
_SC_LOGIN_NAME_MAX	LOGNAME_MAX + 1	Max length of login name.
_SC_MQ_OPEN_MAX	MQ_OPEN_MAX	Max number of open message
		queues a process may hold.
_SC_MQ_PRIO_MAX	MQ_PRIO_MAX	Max number of message priorities
		supported by implementation.
_SC_RTSIG_MAX	RTSIG_MAX	Max number of realtime signals
		reserved for application use
		in this implementation.
_SC_SEM_NSEMS_MAX	SEM_NSEMS_MAX	Max number of semaphores
		that a process may have.
_SC_SEM_VALUE_MAX	SEM_VALUE_MAX	Max value a semaphore may have.
_SC_SIGQUEUE_MAX	SIGQUEUE_MAX	Max number of queued signals
		that a process may send and have
		pending at receiver(s) at a time.
_SC_TIMER_MAX	TIMER_MAX	Max number of timers per process
		supported by implementation.
_SC_ASYNCHRONOUS_IO	_POSIX_ASYNCHRONOUS_IO	Supports Asynchronous I/O.
_SC_FSYNC	_POSIX_FSYNC	Supports File Synchronization.
_SC_MAPPED_FILES	_POSIX_MAPPED_FILES	Supports Memory Mapped Files.
_SC_MEMLOCK	_POSIX_MEMLOCK	Supports Process Memory Locking.
_SC_MEMLOCK_RANGE	_POSIX_MEMLOCK_RANGE	Supports Range Memory Locking.
_SC_MEMORY_PROTECTION	_POSIX_MEMORY_PROTECTION	Supports Memory Protection.
_SC_MESSAGE_PASSING	_POSIX_MESSAGE_PASSING	Supports Message Passing.
_SC_PRIORITIZED_IO	_POSIX_PRIORITIZED_IO	Supports Prioritized I/O.
_SC_PRIORITY_SCHEDULING	_POSIX_PRIORITY_SCHEDULING	Supports Process Scheduling
_SC_REALTIME_SIGNALS	_POSIX_REALTIME_SIGNALS	Supports Realtime Signals.
_SC_SEMAPHORES	_POSIX_SEMAPHORES	Supports Semaphores.
_SC_SHARED_MEMORY_	_POSIX_SHARED_MEMORY_	Supports Shared Memory
OBJECTS	OBJECTS	Objects.
_SC_SYNCHRONIZED_IO	_POSIX_SYNCHRONIZED_IO	Supports Synchronized I/O.
_SC_TIMERS	_POSIX_TIMERS	Supports Timers.
_SC_THREAD_DESTRUCTOR_	PTHREAD_DESTRUCTOR_	Number attempts made to destroy
ITERATIONS	ITERATIONS	thread-specific data on thread exit.
_SC_THREAD_KEYS_MAX	PTHREAD_KEYS_MAX	Max number of data keys
		per process.
_SC_THREAD_STACK_MIN	PTHREAD_STACK_MIN	Min byte size of thread
		stack storage.
_SC_THREAD_THREADS_MAX	PTHREAD_THREADS_MAX	Max number of threads per process.
_SC_TTY_NAME_MAX	TTYNAME_MAX	Max length of tty device name.
_SC_THREADS	_POSIX_THREADS	Supports Threads option.

_SC_THREAD_ATTR_STACKADDR	_POSIX_THREAD_ATTR_STACKADDR
	Supports Thread Stack Address Attribute option.
_SC_THREAD_ATTR_STACKSIZE	_POSIX_THREAD_ATTR_STACKSIZE
	Supports Thread Stack Size Attribute option.
_SC_THREAD_PRIORITY_SCHEDULING	_POSIX_THREAD_PRIORITY_SCHEDULING
	Supports Thread Execution Scheduling option.
_SC_THREAD_PRIO_INHERIT	_POSIX_THREAD_PRIO_INHERIT
	Supports Priority Inheritance option.
_SC_THREAD_PRIO_PROTECT	_POSIX_THREAD_PRIO_PROTECT
	Supports Priority Protection option.
_SC_THREAD_PROCESS_SHARED	_POSIX_THREAD_PROCESS_SHARED
	Supports Process-Shared Synchronization option.
_SC_THREAD_SAFE_FUNCTIONS	_POSIX_THREAD_SAFE_FUNCTIONS
	Supports Thread-Safe Functions option.

The following table lists the names and return values for platform-specific system variables.

Name	Return Value
	SPARC , x86	PowerPC
_SC_COHER_BLKSZ	EINVAL	Cache coherency size in bytes.
_SC_SPLIT_CACHE	EINVAL	0 for non-split or 1 for split.
_SC_ICACHE_SZ	EINVAL	Size of icache in bytes.
_SC_DCACHE_SZ	EINVAL	Size of data cache in bytes.
_SC_ICACHE_LINESZ	EINVAL	Instruction cache line size in bytes.
_SC_DCACHE_LINESZ	EINVAL	Data cache line size in bytes.
_SC_ICACHE_BLKSZ	EINVAL	Block size invalidated in icache by
		icbi in bytes.
_SC_DCACHE_BLKSZ	EINVAL	Block size for dcbz, dcbst, dcbf
		and dcbi in bytes.
_SC_DCACHE_TBLKSZ	EINVAL	Block size for dcache prefetch by dcbt
		and dcbtst in bytes.
_SC_ICACHE_ASSOC	EINVAL	Icache associativity (2 = 2-way...).
_SC_DCACHE_ASSOC	EINVAL	Dcache associativity (2 = 2-way...).
_SC_PPC_GRANULE_SZ	EINVAL	Granule size for reservations by lwarx
		in bytes.
_SC_PPC_TB_TICKSPSECH	EINVAL	Currently returns 0 (reserved for future expansion).
_SC_PPC_TB_TICKSPSECL	EINVAL	Returns the rate at which the timebase
		is updated.

Return Values

See Also

Notes

Multiplying sysconf(_SC_PHYS_PAGES ) or sysconf(_SC_AVPHYS_PAGES ) by sysconf(_SC_PAGESIZE ) to determine memory amount in bytes can exceed the maximum values representable in a long or unsigned long.

_SC_PHYS_PAGES and _SC_AVPHYS_PAGES are specific to Solaris 2.3 and later releases.

The value of CLK_TCK may be variable and it should not be assumed that CLK_TCK is a compile-time constant.

Calling sysconf() with _SC_THREAD_KEYS_MAX or _SC_THREAD_THREADS_MAX returns -1, because no maximum limit can be determined. The system supports at least the minimum values defined by _POSIX_THREAD_KEYS_MAX and _POSIX_THREAD_THREADS_MAX and can support higher values depending upon system resources.

_SC_THREAD_PRIO_INHERIT and _SC_THREAD_PRIO_PROTECT are currently not supported, so sysconf() with these arguments returns -1.

Table of Contents

• Name
• Synopsis
• Availability
• MT-Level
• Description
• Return Values
• See Also
• Notes