ISCNTRL(3POSIX)

🎀 ISCNTRL(3POSIX) — the POSIX Programmer's Manual, bestie edition 🎀

okay so hi. welcome to the POSIX Programmer's Manual page for iscntrl, and yes this is the whole thing, no skips, no cuts, we're doing all of it 💖

💬 PROLOG (the lil disclaimer bestie)

So like, heads up: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ — so consult the corresponding Linux manual page for details of Linux behavior — or, plot twist, the interface may not be implemented on Linux at all. 🙈

---

✨ NAME ✨

iscntrl, iscntrl_l — test for a control character

---

🌸 SYNOPSIS 🌸

#include <ctype.h>

int iscntrl(int c);
int iscntrl_l(int c, locale_t locale);

---

💅 DESCRIPTION 💅

okay so, for iscntrl(): 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 — like, not on purpose at all. This volume of POSIX.1‐2017 defers to the ISO C standard. periodt.

The iscntrl() and iscntrl_l() functions shall test whether c is a character of class cntrl 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 a type int, the value of which the application shall ensure is a character representable as an unsigned char or equal to the value of the macro EOF.

⚠️ bestie. if the argument has any other value, the behavior is undefined. not "kinda weird", not "a little off" — UNDEFINED. do not test it. do not pass it. do not collect $200. 💀

And also: the behavior is undefined if the locale argument to iscntrl_l() is the special locale object LC_GLOBAL_LOCALE or is not a valid locale object handle. so like, valid handles only, mwah 🫶

---

🔥 RETURN VALUE 🔥

The iscntrl() and iscntrl_l() functions shall return non-zero if c is a control character; otherwise, they shall return 0. that's it, that's the whole vibe check. ✨

---

💀 ERRORS 💀

No errors are defined.

The following sections are informative.

---

🦋 EXAMPLES 🦋

None. (i know. tragic. nothing to show you. the girls are simply not demoing today 😭)

---

🌈 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. like, stay in your lane, use the approved girls, iykyk 💅

---

⭐ RATIONALE ⭐

None.

---

🧚 FUTURE DIRECTIONS 🧚

None.

---

👑 SEE ALSO 👑

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

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

---

💜 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 .

---

and that's the whole page bestie, no cap 🫶 this lil icon was brought to you by IEEE/The Open Group, dated 2017, filed under ISCNTRL(3POSIX). go forth and classify your characters responsibly 💖✨🎀