iscntrl, iscntrl_l - test for a control character
int iscntrl(int c);
[CX] int iscntrl_l(int c, locale_t locale);
For iscntrl(): [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 POSIX.1-2017 defers to the ISO C standard.
The iscntrl() [CX] and iscntrl_l() functions shall test whether c is a character of class cntrl in the current locale, [CX] or in the locale represented by locale, respectively; see XBD 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. If the argument has any other value, the behavior is undefined.
[CX] 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.
The iscntrl() [CX] and iscntrl_l() functions shall return non-zero if c is a control character; otherwise, they shall return 0.
No errors are defined.
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.
isalnum, isalpha, isblank, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit, setlocale, uselocale
XBD Locale, <ctype.h>, <locale.h>
First released in Issue 1. Derived from Issue 1 of the SVID.
The normative text is updated to avoid use of the term "must" for application requirements.
The iscntrl_l() function is added from The Open Group Technical Standard, 2006, Extended API Set Part 4.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0283 , XSH/TC1-2008/0284 , and XSH/TC1-2008/0285  are applied.
return to top of page