C in a Nutshell

Name

islower

Synopsis

Ascertains whether a given character is a lowercase letter

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

The function islower() tests whether its character argument is a lowercase letter. Which characters are letters and which letters are lowercase both depend on the current locale setting for the category LC_CTYPE, which you can query or change using the setlocale() function.

If the character is a lowercase letter, islower() returns a nonzero value (that is, true); if not, the function returns 0 (false).

In the default locale C, the truth values of isupper() and islower() are mutually exclusive for the alphabetic characters. However, other locales may have alphabetic characters for which both isupper() and islower() return true, or characters which are alphabetic, but are neither upper- nor lowercase.

Example

See the example for isprint() in this chapter.

See Also

isupper(), tolower(), toupper(); the corresponding C99 function for wide characters, iswlower(); isalnum(), isalpha(), isblank(), iscntrl(), isdigit(), isgraph(), isprint(), ispunct(), isspace(), isxdigit(), setlocale()