sysconf(3C)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | ATTRIBUTES | SEE ALSO | NOTES

NAME

sysconf- get configurable system variables

SYNOPSIS

#include <unistd.h>

long sysconf(int name);

DESCRIPTION

The sysconf() function provides a method for an 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 on the SPARC and x86 platforms.

Name	Return Value	Meaning
_SC_2_C_BIND	_POSIX2_C_BIND	Supports the C language binding option
_SC_2_C_DEV	_POSIX2_C_DEV	Supports the C language development utilities option
_SC_2_C_VERSION	_POSIX2_C_VERSION	Integer value indicating version of ISO POSIX-2 standard (Commands)
_SC_2_CHAR_TERM	_POSIX2_CHAR_TERM	Supports at least one terminal
_SC_2_FORT_DEV	_POSIX2_FORT_DEV	Supports FORTRAN Development Utilities Option
_SC_2_FORT_RUN	_POSIX2_FORT_RUN	Supports FORTRAN Run-time Utilities Option
_SC_2_LOCALEDEF	_POSIX2_LOCALEDEF	Supports the creation of locales by the localedef utility
_SC_2_SW_DEV	_POSIX2_SW_DEV	Supports the Software Development Utility Option
_SC_2_UPE	_POSIX2_UPE	Supports the User Portability Utilities Option
_SC_2_VERSION	_POSIX2_VERSION	Integer value indicating version of ISO POSIX-2 standard (C language binding)
_SC_AIO_LISTIO_MAX	AIO_LISTIO_MAX	Max number of I/O operations in a single list I/O call supported
_SC_AIO_MAX	AIO_MAX	Max number of outstanding asynchronous I/O operations supported
SC_AIO_PRIO_DELTA_ MAX	AIO_PRIO_DELTA_MAX	Max amount by which a process can decrease its asynchronous I/O priority level from its own scheduling priority
_SC_ARG_MAX	ARG_MAX	Max size of argv[] plus envp[]
_SC_ASYNCHRONOUS_IO	_POSIX_ASYNCHRONOUS_ IO	Supports Asynchronous I/O
_SC_ATEXIT_MAX	ATEXIT_MAX	Max number of functions that may be registered with atexit()
_SC_AVPHYS_PAGES		Number physical memory pages not currently in use by system
_SC_BC_BASE_MAX	BC_BASE_MAX	Maximum obase values allowed by the bc utility
_SC_BC_DIM_MAX	BC_DIM_MAX	Max number of elements permitted in array by bc
_SC_BC_SCALE_MAX	BC_SCALE_MAX	Max scale value allowed by bc
_SC_BC_STRING_MAX	BC_STRING_MAX	Max length of string constant allowed by bc
_SC_CHILD_MAX	CHILD_MAX	Max processes allowed to a UID
_SC_CLK_TCK	CLK_TCK	Ticks per second (clock_t)
_SC_COLL_WEIGHTS_MAX	COLL_WEIGHTS_MAX	Max number of weights that can be assigned to entry of the LC_COLLATE order keyword in locale definition file
_SC_DELAYTIMER_MAX	DELAYTIMER_MAX	Max number of timer expiration overruns
_SC_EXPR_NEST_MAX	EXPR_NEST_MAX	Max number of expressions that can be listed within parentheses by the expr utility
_SC_FSYNC	_POSIX_FSYNC	Supports File Synchronization
_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_IOV_MAX	IOV_MAX	Max number of iovec structures that one process has available for use with readv() and writev()
_SC_JOB_CONTROL	_POSIX_JOB_CONTROL	Job control supported
_SC_LINE_MAX	LINE_MAX	Max length of input line
_SC_LOGIN_NAME_MAX	LOGNAME_MAX + 1	Max length of login name.
_SC_LOGNAME_MAX	LOGNAME_MAX
_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_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
_SC_NGROUPS_MAX	NGROUPS_MAX	Max simultaneous groups to which one may belong
_SC_NPROCESSORS_CONF		Number of processors configured
_SC_NPROCESSORS_ONLN		Number of processors online
_SC_OPEN_MAX	OPEN_MAX	Max open files per process
_SC_PAGESIZE	PAGESIZE	System memory page size
_SC_PAGE_SIZE	PAGESIZE	Same as _SC_PAGESIZE
_SC_PASS_MAX	PASS_MAX	Max number of significant bytes in a password
_SC_PHYS_PAGES		Total number of pages of physical memory in system
_SC_PRIORITIZED_IO	_POSIX_PRIORITIZED_IO	Supports Prioritized I/O
_SC_PRIORITY_ SCHEDULING	_POSIX_PRIORITY_ SCHEDULING	Supports Process Scheduling
_SC_RE_DUP_MAX	RE_DUP_MAX	Max number of repeated
_SC_REALTIME_SIGNALS	_POSIX_REALTIME_ SIGNALS	Supports Realtime Signals.
_SC_RTSIG_MAX	RTSIG_MAX	Max number of realtime signals reserved for application use
_SC_SAVED_IDS	_POSIX_SAVED_IDS	Saved IDs (seteuid()) supported?
_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_SEMAPHORES	_POSIX_SEMAPHORES	Supports Semaphores
_SC_SHARED_MEMORY_ OBJECTS	_POSIX_SHARED_MEMORY_ OBJECTS	Supports Shared MemoryObjects
_SC_SIGQUEUE_MAX	SIGQUEUE_MAX	Max number of queued signals a process may send and have pending at receiver(s) at a time.
_SC_STREAM_MAX	STREAM_MAX	Number of streams one processed can have open at a time
_SC_SYNCHRONIZED_ IO	_POSIX_SYNCHRONIZED_ IO	Supports Synchronized I/O.
_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_DESTRUCTOR_ ITERATIONS	PTHREAD_DESTRUCTOR_ ITERATIONS	Number attempts made to destroy thread-specific data on thread exit
_SC_THREAD_KEYS_MAX	PTHREAD_KEYS_MAX	Max number of data keys per process
_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_PRIORITY_ SCHEDULING	_POSIX_THREAD_PRIORITY_ SCHEDULING	Supports Thread Execution Scheduling 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
_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_THREADS	_POSIX_THREADS	Supports Threads option
_SC_TIMER_MAX	TIMER_MAX	Max number of timers per process
_SC_TIMERS	_POSIX_TIMERS	Supports Timers
_SC_TTY_NAME_MAX	TTYNAME_MAX	Max length of tty device name
_SC_TZNAME_MAX	TZNAME_MAX	Max number of bytes supported for name of a time zone
_SC_VERSION	_POSIX_VERSION	POSIX.1 version supported occurrences of a regular expression permitted when using the interval notation \{m,n\}
_SC_XBS5_ILP32_OFF32	_XBS_ILP32_OFF32	Supports X/Open ILP32 w/32-bit offset build environment
_SC_XBS5_ILP32_OFFBIG	_XBS5_ILP32_OFFBIG	Supports X/Open LP32 w/64-bit offset build environment
_SC_XBS5_LP64_OFF64	_XBS5_LP64_OFF64	Supports X/Open LP64, 64-bit offset build environment
_SC_XBS5_LPBIG_OFFBIG	_XBS5_LP64_OFF64	Same as _SC_XBS5_LP64_OFF64
_SC_XOPEN_CRYPT	_XOPEN_CRYPT	Supports X/Open Encryption Feature Group
_SC_XOPEN_ENH_I18N	_XOPEN_ENH_I18N	Supports X/Open Enhanced Internationalization Feature Group
_SC_XOPEN_LEGACY	_XOPEN_LEGACY	Supports X/Open Legacy Feature Group
_SC_XOPEN_REALTIME	_XOPEN_REALTIME	Supports X/Open POSIX Realtime Feature Group
_SC_XOPEN_REALTIME_ THREADS	_XOPEN_REALTIME_ THREADS	Supports X/Open POSIX Reatime Threads Feature Group
_SC_XOPEN_SHM	_XOPEN_SHM	Supports X/Open Shared Memory Feature Group
_SC_XOPEN_UNIX	_XOPEN_UNIX	Supports X/Open CAE Specification, August 1994, System Interfaces and Headers, Issue 4, Version 2
_SC_XOPEN_VERSION	_XOPEN_VERSION	Integer value indicating version of X/Open Portability Guide to which implementation conforms
_SC_XOPEN_XCU_VERSION	_XOPEN_XCU_VERSION	Integer value indicating version of XCU specification to which implementation conforms

RETURN VALUES

Upon successful completion, sysconf() returns the current variable value on the system. The value returned will not be more restrictive than the corresponding value described to the application when it was compiled with the implementation's <limits.h>, <unistd.h> or <time.h>. The value will not change during the lifetime of the calling process.

If name is an invalid value, sysconf() returns -1 and sets errno to indicate the error. If the variable corresponding to name is associated with functionality that is not supported by the system, sysconf() returns -1 without changing the value of errno.

Calling sysconf() with _SC_THREAD_KEYS_MAX, _SC_THREAD_THREADS_MAX, or _SC_THREAD_DESTRUCTOR_ITERATIONS returns -1 without setting errno, because no maximum limit can be determined. The system supports at least the minimum values defined by _POSIX_THREAD_KEYS_MAX, _POSIX_THREAD_THREADS_MAX, and _POSIX_THREAD_DESTRUCTOR_ITERATIONS and can support higher values depending upon system resources.

The following SPARC and x86 platform variables return EINVAL:

_SC_COHER_BLKSZ	_SC_DCACHE_ASSOC
_SC_DCACHE_BLKSZ	_SC_DCACHE_LINESZ
_SC_DCACHE_SZ	_SC_DCACHE_TBLKSZ
_SC_ICACHE_ASSOC	_SC_ICACHE_BLKSZ
_SC_ICACHE_LINESZ	_SC_ICACHE_SZ
_SC_SPLIT_CACHE

ERRORS

The sysconf() function will fail if:

EINVAL

The value of the name argument is invalid.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Architecture	SPARC and x86
MT-Level	MT-Safe, Async-Signal-Safe

SEE ALSO

fpathconf(2), seteuid(2), setrlimit(2), attributes(5), standards(5)

NOTES

A call to setrlimit() may cause the value of OPEN_MAX to change.

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.

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

The _SC_PHYS_PAGES and _SC_AVPHYS_PAGES variables are specific to Solaris 2.3 or compatible releases.

The _SC_THREAD_PRIO_INHERIT and _SC_THREAD_PRIO_PROTECT variables are currently not supported. A call to sysconf() with these variables as arguments returns -1.

SunOS 5.7  Last Revised 10 Mar 1998

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | ATTRIBUTES | SEE ALSO | NOTES