3.6 islower—lowercase character predicate

Synopsis

     #include <ctype.h>
     int islower(int c);
     

Description
islower is a macro which classifies ASCII integer values by table lookup. It is a predicate returning non-zero for minuscules (lowercase alphabetic characters), and 0 for other characters. It is defined only if c is representable as an unsigned char or if c is EOF.

You can use a compiled subroutine instead of the macro definition by undefining the macro using `#undef islower'.

Returns
islower returns non-zero if c is a lowercase letter (a–z).

Portability
islower is ANSI C.

No supporting OS subroutines are required.