std::isprint (3) - Linux Man Pages

std::isprint: std::isprint

NAME

std::isprint - std::isprint

Synopsis


Defined in header <cctype>
int isprint( int ch );


Checks if ch is a printable character as classified by the currently installed C locale. In the default, "C" locale, the following characters are printable:


* digits (0123456789)
* uppercase letters (ABCDEFGHIJKLMNOPQRSTUVWXYZ)
* lowercase letters (abcdefghijklmnopqrstuvwxyz)
* punctuation characters (!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~)
* space ()


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 can be printed, zero otherwise.

Notes


Like all other functions from <cctype>, the behavior of std::isprint 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_isprint(char ch)
  {
      return std::isprint(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_prints(const std::string& s)
  {
      return std::count_if(s.begin(), s.end(),
                        // static_cast<int(*)(int)>(std::isprint) // wrong
                        // [](int c){ return std::isprint(c); } // wrong
                        // [](char c){ return std::isprint(c); } // wrong
                           [](unsigned char c){ return std::isprint(c); } // correct
                          );
  }

Example


// Run this code


  #include <iostream>
  #include <cctype>
  #include <clocale>


  int main()
  {
      unsigned char c = '\xa0'; // the non-breaking space in ISO-8859-1


      std::cout << "isprint(\'\\xa0\', default C locale) returned "
                 << std::boolalpha << (bool)std::isprint(c) << '\n';


      std::setlocale(LC_ALL, "en_GB.iso88591");
      std::cout << "isprint(\'\\xa0\', ISO-8859-1 locale) returned "
                << std::boolalpha << (bool)std::isprint(c) << '\n';
  }

Output:


  isprint('\xa0', default C locale) returned false
  isprint('\xa0', ISO-8859-1 locale) returned true

See also


                     checks if a character is classified as printable by a locale
isprint(std::locale) (function template)
                     checks if a wide character is a printing character
iswprint (function)


ASCII values iscntrl isprint isspace isblank isgraph ispunct isalnum isalpha isupper islower isdigit isxdigit
decimal hexadecimal octal characters iswcntrl iswprint iswspace iswblank iswgraph iswpunct iswalnum iswalpha iswupper iswlower iswdigit iswxdigit


0–8 \x0–\x8 \0–\10 control codes (NUL, etc.) ≠0 0 0 0 0 0 0 0 0 0 0 0
9 \x9 \11 tab (\t) ≠0 0 ≠0 ≠0 0 0 0 0 0 0 0 0
10–13 \xA–\xD \12–\15 whitespaces (\n, \v, \f, \r) ≠0 0 ≠0 0 0 0 0 0 0 0 0 0
14–31 \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
33–47 \x21–\x2F \41–\57 !"#$%&'()*+,-./ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
48–57 \x30–\x39 \60–\71 0123456789 0 ≠0 0 0 ≠0 0 ≠0 0 0 0 ≠0 ≠0
58–64 \x3A–\x40 \72–\100:;<=>?@ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
65–70 \x41–\x46 \101–\10ABCDEF 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 ≠0
71–90 \x47–\x5A \107–\13GHIJKLMNOP 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0
                              QRSTUVWXYZ
91–96 \x5B–\x60 \133–\14[\]^_` 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
97–102\x61–\x66 \141–\14abcdef 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 ≠0
103–12\x67–\x7A \147–\17ghijklmnop 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0
                              qrstuvwxyz
123–12\x7B–\x7E \172–\17{|}~ 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0
127 \x7F \177 backspace character (DEL) ≠0 0 0 0 0 0 0 0 0 0 0 0