SYSCONF(3)                OpenBSD Programmer's Manual               SYSCONF(3)

NAME
     sysconf - get configurable system variables

SYNOPSIS
     #include <unistd.h>

     long
     sysconf(int name);

DESCRIPTION
     This interface is defined by IEEE Std 1003.1-1988 (``POSIX'').  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 arguments to exec(3) (including the environ-
             ment).

     _SC_CHILD_MAX
             The maximum number of simultaneous processes per user ID.

     _SC_CLK_TCK
             The number of clock ticks per second.

     _SC_NGROUPS_MAX
             The maximum number of supplemental groups.

     _SC_OPEN_MAX
             The maximum number of open files per user ID.

     _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
             time zone.

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

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

     _SC_VERSION
             The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
             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
             parentheses 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 Op-
             tion, 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_PAGESIZE
             The size of a system page in bytes.

     _SC_FSYNC
             Return 1 if the system supports the File Synchronisation Option,
             otherwise -1.

     _SC_XOPEN_SHM
             Return 1 if the system supports the Shared Memory Option, other-
             wise -1.

     _SC_SEM_NSEMS_MAX
             The maximum number of semaphores in the system or -1 if the sys-
             tem does not support the Semaphores Option.

     _SC_SEM_VALUE_MAX
             The maximum value a semaphore may have or -1 if the system does
             not support the Semaphores Option.

     _SC_PHYS_PAGES
             The number of pages of physical memory.

     _SC_AVPHYS_PAGES
             The number of pages of physical memory not currently in use by
             the system.

     _SC_GETGR_R_SIZE_MAX
             The maximum size of the data buffer for the getgrgid_r() and
             getgrnam_r() functions.

     _SC_GETPW_R_SIZE_MAX
             The maximum size of the data buffer for the getgrgid_r() and
             getgrnam_r() functions.

     _SC_LOGIN_NAME_MAX
             The maximum length of a login name.

     _SC_THREAD_SAFE_FUNCTIONS
             The level of support for thread-safe (re-entrant) functions.

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 er-
     ror may be reported:

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

SEE ALSO
     pathconf(2), sysctl(3)

STANDARDS
     The sysconf() function conforms to IEEE Std 1003.1-1988 (``POSIX'').

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.

OpenBSD 4.5                      June 25, 2008                               3