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ISALNUM(3) Library Functions Manual ISALNUM(3)

isalnum, isalnum_lalphanumeric single-byte character test

#include <ctype.h>

isalnum(int c);

isalnum_l(int c, locale_t locale);

The () function tests for any character for which isalpha(3) or isdigit(3) is true, and () tests for any character for which isalpha_l(3) or isdigit_l(3) is true.

In the C locale, the complete list of alphanumeric characters is A–Z, a–z, 0, and 1–9. OpenBSD always uses the C locale for these functions, ignoring the global locale, the thread-specific locale, and the locale argument.

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

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).

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

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

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

The argument c must be EOF or representable as an unsigned char; otherwise, the result is undefined.

September 11, 2022 OpenBSD-7.2