The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

#### NAME

> isalnum - test for an alphanumeric character

#### SYNOPSIS

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

#### DESCRIPTION

> [CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

> The isalnum() function shall test whether c is a character of class alpha or digit in the program's current locale; see the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 7, Locale.

> The c argument is an int, the value of which the application shall ensure is representable as an unsigned char or equal to the value of the macro EOF. If the argument has any other value, the behavior is undefined.

#### RETURN VALUE

> The isalnum() function shall return non-zero if c is an alphanumeric character; otherwise, it shall return 0.

#### ERRORS

> No errors are defined.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

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

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> isalpha(), iscntrl(), isdigit(), isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit(), setlocale(), the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 7, Locale, <ctype.h>, <stdio.h>

#### CHANGE HISTORY

> First released in Issue 1. Derived from Issue 1 of the SVID.

#### Issue 6

> The DESCRIPTION is updated to avoid use of the term "must" for application requirements.

End of informative text.

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