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ISALPHA(3) Library Functions Manual ISALPHA(3)

NAME

isalpha, isalpha_lalphabetic single-byte character test

SYNOPSIS

#include <ctype.h>
int
isalpha(int c);
int
isalpha_l(int c, locale_t locale);

DESCRIPTION

The isalpha() and isalpha_l() functions test whether c represents a letter.
In the C locale, the complete list of alphabetic characters is A–Z and a–z. OpenBSD always uses the C locale for these functions, ignoring the global locale, the thread-specific locale, and the locale argument.

RETURN VALUES

These functions return zero if the character tests false or non-zero if the character tests true.

ENVIRONMENT

On systems supporting non-ASCII single-byte character encodings, these functions may return non-zero for additional characters, and the results of isalnum() may depend on the LC_CTYPE locale(1), but they never return non-zero for any character for which iscntrl(3), isdigit(3), ispunct(3), or isspace(3) is true.

SEE ALSO

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

STANDARDS

The isalpha() function conforms to ANSI X3.159-1989 (“ANSI C89”), and isalpha_l() to IEEE Std 1003.1-2008 (“POSIX.1”).

HISTORY

The isalpha() function first appeared in Version 7 AT&T UNIX, and isalpha_l() has been available since OpenBSD 6.2.

CAVEATS

The argument c must be EOF or representable as an unsigned char; otherwise, the result is undefined.
September 5, 2017 OpenBSD-current