NAME    [Toc]    [Back]

     sysconf - get configurable system variables

SYNOPSIS    [Toc]    [Back]

     #include <unistd.h>

     long
     sysconf(int name);

DESCRIPTION    [Toc]    [Back]

     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 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 arguments to exec(3) (including
the environment).


     _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
             timezone.

     _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-userID is available,
 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
             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_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, otherwise
 -1.

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

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

RETURN VALUES    [Toc]    [Back]

     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    [Toc]    [Back]

     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    [Toc]    [Back]

     pathconf(2), sysctl(3)

STANDARDS    [Toc]    [Back]

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

HISTORY    [Toc]    [Back]

     The sysconf() function first appeared in 4.4BSD.

BUGS    [Toc]    [Back]

     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     3.6                          April      19,      1994