ISALNUM(3P)

💖 PROLOG 💖

okay so real talk before we get into it: this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ (so like, go check the corresponding Linux manual page for the Linux deets, bestie), or the interface might not even be implemented on Linux at all. just so you know going in. 💀

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✨ NAME ✨

isalnum, isalnum_l — test for an alphanumeric character

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🎀 SYNOPSIS 🎀

#include <ctype.h>

int isalnum(int c);
int isalnum_l(int c, locale_t locale);

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🦋 DESCRIPTION 🦋

so for isalnum(): 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 — it's giving "we didn't mean it, fr". this volume of POSIX.1‐2017 defers to the ISO C standard. 👑

The isalnum() and isalnum_l() functions shall test whether c is a character of class alpha or digit in the current locale, or in the locale represented by locale, respectively; see the Base Definitions volume of POSIX.1‐2017, 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. 🚨 like, do not pass it weird stuff, i'm begging.

The behavior is undefined if the locale argument to isalnum_l() is the special locale object LC_GLOBAL_LOCALE or is not a valid locale object handle. no cap, that's just not a thing you do.

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💅 RETURN VALUE 💅

The isalnum() and isalnum_l() functions shall return non-zero if c is an alphanumeric character; otherwise, they shall return 0. simple as that, periodt.

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🌸 ERRORS 🌸

No errors are defined.

The following sections are informative. (iykyk, that means the vibe is "extra context, not law")

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🌈 EXAMPLES 🌈

None. literally nothing. iconic of them honestly. 🙈

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🍓 APPLICATION USAGE 🍓

To ensure applications portability, especially across natural languages, only these functions and the functions in the reference pages listed in the SEE ALSO section should be used for character classification. don't go rogue with your own classification, bestie, it will not travel well. ✈️

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💜 RATIONALE 💜

None.

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⭐ FUTURE DIRECTIONS ⭐

None.

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🔥 SEE ALSO 🔥

• isalpha()
• isblank()
• iscntrl()
• isdigit()
• isgraph()
• islower()
• isprint()
• ispunct()
• isspace()
• isupper()
• isxdigit()
• setlocale()
• uselocale()

The Base Definitions volume of POSIX.1‐2017, Chapter 7, Locale, <ctype.h>, <stdio.h>

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👑 COPYRIGHT 👑

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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and that's the whole page, bestie!! brought to you by IEEE/The Open Group, dated 2017, from the POSIX Programmer's Manual (aka ISALNUM(3P)). go forth and classify your characters responsibly. mwah. 💋✨