ISALPHA(3) Library Functions Manual ISALPHA(3)

isalpha
alphabetic character test

Standard C Library (libc, -lc)

#include <ctype.h>

int
isalpha(int c);

The isalpha() function tests for any character for which isupper(3) or islower(3) is true and for which none of iscntrl(3), isdigit(3), ispunct(3), or isspace(3) is true. In the ``C'' locale, isalpha() returns true only for the characters for which isupper(3) or islower(3) is true.

The isalpha() function returns zero if the character tests false and returns non-zero if the character tests true.

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

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

The argument to isalpha() must be EOF or representable as an unsigned char; otherwise, the behavior is undefined. See the CAVEATS section of ctype(3) for more details.
April 17, 2008 NetBSD 9.2