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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 charac- ters are the characters with the codes 0x00-0x1F and 0x7F. The behavior is undefined if the value of ch is not representable as unsigned 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 other- wise. 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 argument 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 <iostream> #include <cctype> #include <clocale> int main() { unsigned char c = '\x94'; // the control code CCH in ISO-8859-1 std::cout << "iscntrl(\'\\x94\', default C locale) returned " << std::boolalpha << (bool)std::iscntrl(c) << '\n'; std::setlocale(LC_ALL, "en_GB.iso88591"); std::cout << "iscntrl(\'\\x94\', ISO-8859-1 locale) returned " << std::boolalpha << (bool)std::iscntrl(c) << '\n'; } 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 con- trol character by a iscntrl(std::locale) locale (function template) iswcntrl checks if a wide character is a control charac- ter (function) ASCII values characters iscntrl isprint is- space isblank isgraph ispunct isalnum isalpha isupper islower isdigit isxdigit decimal hexadecimal octal iswcntrl iswprint iswspace iswblank iswgraph iswpunct iswalnum iswalpha iswupper iswlower iswdigit iswxdigit 08 \x0\x8 \0\10 control codes 0 0 0 0 0 0 0 0 0 0 0 0 (NUL, etc.) 9 \x9 \11 tab (\t) 0 0 0 0 0 0 0 0 0 0 0 0 whitespaces 1013 \xA\xD \12\15 (\n, \v, \f, 0 0 0 0 0 0 0 0 0 0 0 0 \r) 1431 \xE\x1F \16\37 control codes 0 0 0 0 0 0 0 0 0 0 0 0 32 \x20 \40 space 0 0 0 0 0 0 0 0 0 0 0 0 3347 \x21\x2F \41\57 !"#$%&'()*+,-./ 0 0 0 0 0 0 0 0 0 0 0 0 4857 \x30\x39 \60\71 0123456789 0 0 0 0 0 0 0 0 0 0 0 0 5864 \x3A\x40 \72\100 :;<=>?@ 0 0 0 0 0 0 0 0 0 0 0 0 6570 \x41\x46 \101\106 ABCDEF 0 0 0 0 0 0 0 0 0 0 0 0 7190 \x47\x5A \107\132 GHIJKLMNOP 0 0 0 0 0 0 0 0 0 0 0 0 QRSTUVWXYZ 9196 \x5B\x60 \133\140 [\]^_` 0 0 0 0 0 0 0 0 0 0 0 0 97102 \x61\x66 \141\146 abcdef 0 0 0 0 0 0 0 0 0 0 0 0 103122 \x67\x7A \147\172 ghijklmnop 0 0 0 0 0 0 0 0 0 0 0 0 qrstuvwxyz 123126 \x7B\x7E \172\176 {|}~ 0 0 0 0 0 0 0 0 0 0 0 0 127 \x7F \177 backspace 0 0 0 0 0 0 0 0 0 0 0 0 character (DEL) http://cppreference.com 2022.07.31 std::iscntrl(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Output: | See also
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