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ISLOWER(3) Library Functions Manual ISLOWER(3)

islowerlower-case character test

#include <ctype.h>

islower(int c);

The () function tests for any lower-case letter for which none of iscntrl(3), isdigit(3), ispunct(3), or isspace(3) is true. In the C locale, islower() returns true only for the characters defined as lower-case letters.

The islower() function returns zero if the character tests false or non-zero if the character tests true.

isalnum(3), isalpha(3), isascii(3), isblank(3), iscntrl(3), isdigit(3), isgraph(3), isprint(3), ispunct(3), isspace(3), isupper(3), isxdigit(3), stdio(3), toascii(3), tolower(3), toupper(3), ascii(7)

The islower() function conforms to ANSI X3.159-1989 (“ANSI C89”).

The islower() function first appeared in Version 7 AT&T UNIX.

The argument to islower() must be EOF or representable as an unsigned char; otherwise, the result is undefined.

July 17, 2013 OpenBSD-5.5