sysconf(3) - NetBSD Manual Pages

SYSCONF(3)                NetBSD Programmer's 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'').  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_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_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_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_STREAM_MAX
             The minimum maximum number of streams that a process may have
             open at any one time.

     _SC_SYNCHRONIZED_IO
             Return 1 if the Synchronized I/O Option is available on this sys-
             tem, 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 of the system supports System V style shared memory,
             otherwise -1.

     _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 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.


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)


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.


STANDARDS

     The sysconf() function conforms to IEEE Std 1003.1-1990 (``POSIX'').


HISTORY

     The sysconf function first appeared in 4.4BSD.

NetBSD 1.5                       June 24, 1999                               3