std::iscntrl(3) C++ Standard Libary std::iscntrl(3) NAME std::iscntrl - std::iscntrl Synopsis Defined in header <cctype> int iscntrl( int ch ); Checks if the given character is a control character as classified by the currently installed C locale. In the default, "C" locale, the control characters are the characters with the codes 0x00-0x1F and 0x7F. The behavior is undefined if the value of ch is not representable as un- signed char and is not equal to EOF. Parameters ch - character to classify Return value Non-zero value if the character is a control character, zero otherwise. Notes Like all other functions from <cctype>, the behavior of std::iscntrl is undefined if the argument's value is neither representable as unsigned char nor equal to EOF. To use these functions safely with plain chars (or signed chars), the argu- ment should first be converted to unsigned char: bool my_iscntrl(char ch) { return std::iscntrl(static_cast<unsigned char>(ch)); } Similarly, they should not be directly used with standard algorithms when the iterator's value type is char or signed char. Instead, convert the value to unsigned char first: int count_cntrls(const std::string& s) { return std::count_if(s.begin(), s.end(), // static_cast<int(*)(int)>(std::iscntrl) // wrong // [](int c){ return std::iscntrl(c); } // wrong // [](char c){ return std::iscntrl(c); } // wrong [](unsigned char c){ return std::iscntrl(c); } // correct ); } Example // Run this code #include <cctype> #include <clocale> #include <iostream> int main() { unsigned char c = '\x94'; // the control code CCH in ISO-8859-1 std::cout << "iscntrl(\'\\x94\', default C locale) returned " << std::boolalpha << !!std::iscntrl(c) << '\n'; std::setlocale(LC_ALL, "en_GB.iso88591"); std::cout << "iscntrl(\'\\x94\', ISO-8859-1 locale) returned " << !!std::iscntrl(c) << '\n'; } Possible output: iscntrl('\x94', default C locale) returned false iscntrl('\x94', ISO-8859-1 locale) returned true See also checks if a character is classified as a control character by a iscntrl(std::locale) locale (function template) iswcntrl checks if a wide character is a control character (function) C documentation for iscntrl ASCII values characters iscntrl isprint isspace isblank isgraph ispunct isalnum isalpha isupper islower isdigit isxdigit decimal hexadecimal octal iswcntrl iswprint iswspace iswblank iswgraph iswpunct iswalnum iswalpha iswupper iswlower iswdigit iswxdigit 0a8 \x0a\x8 \0a\10 control codes a 0 0 0 0 0 0 0 0 0 0 0 0 (NUL, etc.) 9 \x9 \11 tab (\t) a 0 0 a 0 a 0 0 0 0 0 0 0 0 0 whitespaces 10a13 \xAa\xD \12a\15 (\n, \v, \f, a 0 0 a 0 0 0 0 0 0 0 0 0 0 \r) 14a31 \xEa\x1F \16a\37 control codes a 0 0 0 0 0 0 0 0 0 0 0 0 32 \x20 \40 space 0 a 0 a 0 a 0 0 0 0 0 0 0 0 0 33a47 \x21a\x2F \41a\57 !"#$%&'()*+,-./ 0 a 0 0 0 a 0 a 0 0 0 0 0 0 0 48a57 \x30a\x39 \60a\71 0123456789 0 a 0 0 0 a 0 0 a 0 0 0 0 a 0 a 0 58a64 \x3Aa\x40 \72a\100 :;<=>?@ 0 a 0 0 0 a 0 a 0 0 0 0 0 0 0 65a70 \x41a\x46 \101a\106 ABCDEF 0 a 0 0 0 a 0 0 a 0 a 0 a 0 0 0 a 0 71a90 \x47a\x5A \107a\132 GHIJKLMNOP 0 a 0 0 0 a 0 0 a 0 a 0 a 0 0 0 0 QRSTUVWXYZ 91a96 \x5Ba\x60 \133a\140 [\]^_` 0 a 0 0 0 a 0 a 0 0 0 0 0 0 0 97a102 \x61a\x66 \141a\146 abcdef 0 a 0 0 0 a 0 0 a 0 a 0 0 a 0 0 a 0 103a122 \x67a\x7A \147a\172 ghijklmnop 0 a 0 0 0 a 0 0 a 0 a 0 0 a 0 0 0 qrstuvwxyz 123a126 \x7Ba\x7E \172a\176 {|}~ 0 a 0 0 0 a 0 a 0 0 0 0 0 0 0 127 \x7F \177 backspace a 0 0 0 0 0 0 0 0 0 0 0 0 character (DEL) http://cppreference.com 2024.06.10 std::iscntrl(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Possible output: | See also
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