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SYSCONF(3)                 Library Functions Manual                 SYSCONF(3)

NAME
     sysconf -- get configurable system variables

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <&lt;unistd.h>&gt;

     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
     constants for each name value are found in the include file <unistd.h>.

     The available values are as follows:

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

     _SC_ATEXIT_MAX
             The maximum number of functions that may be registered with
             atexit(3).

     _SC_BARRIERS
             The version of IEEE Std 1003.1 (``POSIX.1'') and its Barriers
             option to which the system attempts to conform, otherwise -1.

     _SC_CLOCK_SELECTION
             Return the POSIX version the implementation of the Clock
             Selection Option on this system conforms to, or -1 if
             unavailable.

     _SC_CHILD_MAX
             The maximum number of simultaneous processes per user id.

     _SC_CLK_TCK
             The number of clock ticks per second.

     _SC_FSYNC
             Return 1 if the File Synchronization Option is available on this
             system, otherwise -1.

     _SC_HOST_NAME_MAX
             The maximum size of a hostname, including NULL.

     _SC_IOV_MAX
             The maximum number of iovec structures that a process has
             available for use with preadv(2), pwritev(2), readv(2),
             recvmsg(2), sendmsg(2) or writev(2).

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

     _SC_LOGIN_NAME_MAX
             Returns the size of the storage required for a login name, in
             bytes, including the terminating NUL.

     _SC_MAPPED_FILES
             Return 1 if the Memory Mapped Files Option is available on this
             system, otherwise -1.

     _SC_MEMLOCK
             Return 1 if the Process Memory Locking Option is available on
             this system, otherwise -1.

     _SC_MEMLOCK_RANGE
             Return 1 if the Range Memory Locking Option is available on this
             system, otherwise -1.

     _SC_MEMORY_PROTECTION
             Return 1 if the Memory Protection Option is available on this
             system, otherwise -1.

     _SC_MONOTONIC_CLOCK
             Return the POSIX version the implementation of the Monotonic
             Clock Option on this system conforms to, or -1 if unavailable.

     _SC_NGROUPS_MAX
             The maximum number of supplemental groups.

     _SC_OPEN_MAX
             The maximum number of open files per process.

     _SC_PAGESIZE
             The size of a system page in bytes.

     _SC_PASS_MAX
             The maximum length of the password, not counting NULL.

     _SC_READER_WRITER_LOCKS
             The version of IEEE Std 1003.1 (``POSIX.1'') and its Read-Write
             Locks option to which the system attempts to conform, otherwise
             -1.

     _SC_REGEXP
             Return 1 if POSIX regular expressions are available on this
             system, otherwise -1.

     _SC_SEMAPHORES
             The version of IEEE Std 1003.1 (``POSIX.1'') and its Semaphores
             option to which the system attempts to conform, otherwise -1.

             Availability of the Semaphores option depends on the
             P1003_1B_SEMAPHORE kernel option.

     _SC_SHELL
             Return 1 if POSIX shell is available on this system, otherwise
             -1.

     _SC_SPIN_LOCKS
             The version of IEEE Std 1003.1 (``POSIX.1'') and its Spin Locks
             option to which the system attempts to conform, otherwise -1.

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

     _SC_SYMLOOP_MAX
             The maximum number of symbolic links that may be expanded in a
             path name.

     _SC_SYNCHRONIZED_IO
             Return 1 if the Synchronized I/O Option is available on this
             system, otherwise -1.

     _SC_THREADS
             The version of IEEE Std 1003.1 (``POSIX.1'') and its Threads
             option to which the system attempts to conform, otherwise -1.

     _SC_TIMERS
             The version of IEEE Std 1003.1 (``POSIX.1'') and its Timers
             option to which the system attempts to conform, otherwise -1.

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

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

     _SC_VERSION
             The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
             attempts to comply.

     _SC_XOPEN_SHM
             Return 1 if the X/Open Portability Guide Issue 4, Version 2
             (``XPG4.2'') Shared Memory option is available on this system,
             otherwise -1.

             Availability of the Shared Memory option depends on the SYSVSHM
             kernel option.

     _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
             expression permitted when using interval notation.

     _SC_2_VERSION
             The version of POSIX 1003.2 with which the system attempts to
             comply.

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

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

     _SC_2_CHAR_TERM
             Return 1 if the system supports at least one terminal type
             capable of all operations described in POSIX 1003.2, 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,
             otherwise -1.

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

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

     _SC_GETGR_R_SIZE_MAX
             The minimum size of the buffer passed to getgrgid_r(3) and
             getgrnam_r(3).

     _SC_GETPW_R_SIZE_MAX
             The minimum size of the buffer passed to getpwnam_r(3) and
             getpwuid_r(3).

     _SC_NPROCESSORS_CONF
             The number of processors configured.

     _SC_NPROCESSORS_ONLN
             The number of processors online (capable of running processes).

     _SC_PHYS_PAGES
             The amount of physical memory on the system in _SC_PAGESIZE
             bytes.

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
     functionality that is not supported, -1 is returned and errno is not
     modified.  Otherwise, the current variable value is returned.

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

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

SEE ALSO
     getconf(1), limits(3), sysctl(3)

STANDARDS
     The sysconf() function conforms to IEEE Std 1003.1-1990 (``POSIX.1'').
     The constants _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are not part
     of the standard, but are provided by many systems.

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.

NetBSD 6.1.5                   November 2, 2012                   NetBSD 6.1.5