std::isgraph

 

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

Checks if the given character is graphic (has a graphical representation) as classified by the currently installed C locale. In the default C locale, the following characters are graphic:

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

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 has a graphical representation character, zero otherwise.

Notes

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

Example

Run this code

#include <cctype>
#include <clocale>
#include <iostream>
 
int main()
{
    unsigned char c = '\xb6'; // the character ¶ in ISO-8859-1
 
    std::cout << "isgraph(\'\\xb6\', default C locale) returned "
              << std::boolalpha << (std::isgraph(c) != 0) << '\n';
 
    std::setlocale(LC_ALL, "en_GB.iso88591");
    std::cout << "isgraph(\'\\xb6\', ISO-8859-1 locale) returned "
              << std::boolalpha << (std::isgraph(c) != 0) << '\n';
}

Possible output:

isgraph('\xb6', default C locale) returned false
isgraph('\xb6', ISO-8859-1 locale) returned true

See also

isgraph(std::locale)	checks if a character is classified as graphical by a locale (function template)
iswgraph	checks if a wide character is a graphical character (function)
C documentation for isgraph

ASCII values			characters	iscntrl iswcntrl	isprint iswprint	isspace iswspace	isblank iswblank	isgraph iswgraph	ispunct iswpunct	isalnum iswalnum	isalpha iswalpha	isupper iswupper	islower iswlower	isdigit iswdigit	isxdigit iswxdigit
decimal	hexadecimal	octal
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–\106	ABCDEF	0	≠0	0	0	≠0	0	≠0	≠0	≠0	0	0	≠0
71–90	\x47–\x5A	\107–\132	GHIJKLMNOP QRSTUVWXYZ	0	≠0	0	0	≠0	0	≠0	≠0	≠0	0	0	0
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 qrstuvwxyz	0	≠0	0	0	≠0	0	≠0	≠0	0	≠0	0	0
123–126	\x7B–\x7E	\172–\176	{|}~	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