SYSCONF(3)              NetBSD 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>.

     The available values are as follows:

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

     _SC_ATEXIT_MAX
             The maxmimum 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 Selec-
             tion 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 avail-
             able 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 sys-
             tem, 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 sys-
             tem, 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 expres-
             sion 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 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 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, 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_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).

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 functional-
     ity 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 spec-
     ified 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
     sysctl(3)

STANDARDS
     The sysconf() function conforms to ISO/IEC 9945-1:1990 (``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 5.1                      August 14, 2006                     NetBSD 5.1

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