The POSIX.2 standard specifies certain system limits that you can access
through sysconf that apply to utility behavior rather than the
behavior of the library or the operating system.

The GNU C library defines macros for these limits, and sysconf
returns values for them if you ask; but these values convey no
meaningful information. They are simply the smallest values that
POSIX.2 permits.

— Macro: int BC_BASE_MAX

The largest value of obase that the bc utility is
guaranteed to support.

— Macro: int BC_DIM_MAX

The largest number of elements in one array that the bc utility
is guaranteed to support.

— Macro: int BC_SCALE_MAX

The largest value of scale that the bc utility is
guaranteed to support.

— Macro: int BC_STRING_MAX

The largest number of characters in one string constant that the
bc utility is guaranteed to support.

— Macro: int COLL_WEIGHTS_MAX

The largest number of weights that can necessarily be used in defining
the collating sequence for a locale.

— Macro: int EXPR_NEST_MAX

The maximum number of expressions that can be nested within parenthesis
by the expr utility.

— Macro: int LINE_MAX

The largest text line that the text-oriented POSIX.2 utilities can
support. (If you are using the GNU versions of these utilities, then
there is no actual limit except that imposed by the available virtual
memory, but there is no way that the library can tell you this.)

— Macro: int EQUIV_CLASS_MAX

The maximum number of weights that can be assigned to an entry of the
LC_COLLATE category `order' keyword in a locale definition.
The GNU C library does not presently support locale definitions.

Published under the terms of the GNU General Public License