std::isspace

 

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isalnum isalpha islower isupper isdigit isxdigit	isblank (C++11) iscntrl isgraph isspace isprint ispunct
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Defined in header <cctype>
int isspace(int ch );

Checks if the given character is whitespace character as classified by the currently installed C locale. In the default locale, the whitespace characters are the following:

• space (0x20, ' ')
• form feed (0x0c, '\f')
• line feed (0x0a, '\n')
• carriage return (0x0d, '\r')
• horizontal tab (0x09, '\t')
• vertical tab (0x0b, '\v')

The behavior is undefined if the value of ch is not representable as unsignedchar and is not equal to EOF.

Parameters

ch

-

character to classify

Return value

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

Notes

Like all other functions from <cctype>, the behavior of std::isspace is undefined if the argument's value is neither representable as unsignedchar nor equal to EOF. To use these functions safely with plain chars (or signedchars), the argument should first be converted to unsignedchar:

bool my_isspace(char ch){return std::isspace(static_cast<unsignedchar>(ch));}

Similarly, they should not be directly used with standard algorithms when the iterator's value type is char or signedchar. Instead, convert the value to unsignedchar first:

int count_spaces(conststd::string& s){returnstd::count_if(s.begin(), s.end(), // static_cast<int(*)(int)>(std::isspace) // wrong// [](int c){ return std::isspace(c); } // wrong// [](char c){ return std::isspace(c); } // wrong[](unsignedchar c){return std::isspace(c);}// correct);}

Example

Run this code

#include <cctype>#include <climits>#include <iomanip>#include <iostream>   int main(void){std::cout<<std::hex<<std::setfill('0')<<std::uppercase;for(int ch{}; ch <=UCHAR_MAX;++ch)if(std::isspace(ch))std::cout<<std::setw(2)<< ch <<' ';std::cout<<'\n';}

Output:

09 0A 0B 0C 0D 20

See also

isspace(std::locale)	checks if a character is classified as whitespace by a locale (function template)
iswspace	checks if a wide character is a space character (function)
C documentation for isspace

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