islower—lowercase character predicate #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.