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SYSCONF(3)

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NAME    [Toc]    [Back]

     sysconf -- get configurable system variables

LIBRARY    [Toc]    [Back]

     Standard C Library (libc, -lc)

SYNOPSIS    [Toc]    [Back]

     #include <unistd.h>

     long
     sysconf(int name);

DESCRIPTION    [Toc]    [Back]

     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>.
     Shell programmers who need access to these parameters should use the
     getconf(1) utility.

     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 frequency of the statistics clock in ticks per second.

     _SC_IOV_MAX
	     The maximum number of elements in the I/O vector used by
	     readv(2), writev(2), recvmsg(2), and sendmsg(2).

     _SC_NGROUPS_MAX
	     The maximum number of supplemental groups.

     _SC_NPROCESSORS_CONF
	     The number of processors configured.

     _SC_NPROCESSORS_ONLN
	     The number of processors currently online.

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

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

     _SC_VERSION
	     The version of IEEE Std 1003.1 (``POSIX.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 IEEE Std 1003.2 (``POSIX.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 IEEE Std 1003.2 (``POSIX.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.

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 function sysctl(3).	In addition, the following
     error may be reported:

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

SEE ALSO    [Toc]    [Back]

      
      
     getconf(1), pathconf(2), confstr(3), sysctl(3)

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.

STANDARDS    [Toc]    [Back]

     Except for the fact that values returned by sysconf() may change over the
     lifetime of the calling process, this function conforms to IEEE Std
     1003.1-1988 (``POSIX.1'').

HISTORY    [Toc]    [Back]

     The sysconf() function first appeared in 4.4BSD.


FreeBSD 5.2.1			 June 18, 2001			 FreeBSD 5.2.1
[ Back ]
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