The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


islower - test for a lower-case letter


#include <ctype.h>

int islower(int c);


The islower() function tests whether c is a character of class lower in the program's current locale, see the XBD specification, Locale .

In all cases c is an int, the value of which must be a character representable as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.


The islower() function returns non-zero if c is a lower-case letter; otherwise it returns 0.


No errors are defined.




To ensure applications portability, especially across natural languages, only this function and those listed in the SEE ALSO section should be used for character classification.




isalnum(), isalpha(), iscntrl(), isdigit(), isgraph(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), setlocale(), <ctype.h>, the XBD specification, Locale .


Derived from Issue 1 of the SVID.

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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