The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


isalnum - test for an alphanumeric character


#include <ctype.h>

int isalnum(int c);


The isalnum() function tests whether c is a character of class alpha or digit in the program's current locale, see the XBD specification, Locale .

In all cases c is an int, the value of which must be representable as an unsigned char or must equal the value of the macro EOF. If the argument has any other value, the behaviour is undefined.


The isalnum() function returns non-zero if c is an alphanumeric character; otherwise it returns 0.


No errors are defined.




To ensure application portability, especially across natural languages, only this function and those listed in the SEE ALSO section should be used for character classification.




isalpha(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), setlocale(), <ctype.h>, <stdio.h>, the XBD specification, Locale .


Derived from Issue 1 of the SVID.

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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