std::isprint(3)

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 <cctype>
 #include <clocale>
 #include <iostream>
 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';
 }

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

See also
   isprint(std::locale) checks if a character is classified as printable by a locale
                        (function template)
   iswprint checks if a wide character is a printing character
                        (function)
   C documentation for
   isprint
        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 0–8 \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 10–13 \xA–\xD \12–\15 (\n, \v, \f, ≠0 0 ≠0 0 0 0 0 0 0 0 0 0
                        \r) 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–\106 ABCDEF 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 ≠0 71–90 \x47–\x5A \107–\132 GHIJKLMNOP 0 ≠0 0 0 ≠0 0 ≠0 ≠0 ≠0 0 0 0
                        QRSTUVWXYZ 91–96 \x5B–\x60 \133–\140 [\]^_` 0 ≠0 0 0 ≠0 ≠0 0 0 0 0 0 0 97–102 \x61–\x66 \141–\146 abcdef 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 ≠0 103–122 \x67–\x7A \147–\172 ghijklmnop 0 ≠0 0 0 ≠0 0 ≠0 ≠0 0 ≠0 0 0
                        qrstuvwxyz 123–126 \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)