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 codes0x00-0x1F and0x7F.

The behavior is undefined if the value ofch is not representable asunsignedchar and is not equal toEOF.

[edit]Parameters

[edit]Return value

Non-zero value if the character is a control character, zero otherwise.

[edit]Notes

Like all other functions from<cctype>, the behavior ofstd::iscntrl is undefined if the argument's value is neither representable asunsignedchar nor equal toEOF. To use these functions safely with plainchars (orsignedchars), the argument should first be converted tounsignedchar:

bool my_iscntrl(char ch){return std::iscntrl(static_cast<unsignedchar>(ch));}

Similarly, they should not be directly used with standard algorithms when the iterator's value type ischar orsignedchar. Instead, convert the value tounsignedchar first:

int count_cntrls(conststd::string& s){returnstd::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[](unsignedchar c){return std::iscntrl(c);}// correct);}

[edit]Example

#include <cctype>#include <clocale>#include <iostream> int main(){unsignedchar 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'; }

iscntrl('\x94', default C locale) returned falseiscntrl('\x94', ISO-8859-1 locale) returned true

[edit]See also

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