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ISALNUM(3) Library Functions Manual ISALNUM(3)

isalnum
alphanumeric character test

#include <ctype.h>
int
isalnum(int c);

The isalnum() function tests for any character for which isalpha(3) or isdigit(3) is true.

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

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

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

The argument to isalnum() must be EOF or representable as an unsigned char; otherwise, the result is undefined.
July 17, 2013 OpenBSD-6.1