# std::isspace

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< cpp‎ | string‎ | byte

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 unsigned char 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 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_isspace(char ch)
    {
        return std::isspace(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_spaces(const std::string& s)
    {
        return std::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
                             [](unsigned char 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`

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