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isspace

Defined in header <ctype.h> 
int isspace( int ch );

Checks if the given character is either

  • A standard white-space character:
    • Space (0x20, ' '),
    • Form feed (0x0c, '\f'),
    • Line feed (0x0a, '\n'),
    • Carriage return (0x0d, '\r'),
    • Horizontal tab (0x09, '\t'),
    • Vertical tab (0x0b, '\v'),
  • Or a locale-specific white-space character.

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.

Example

#include <ctype.h>
#include <limits.h>
#include <stdio.h>
 
int main(void)
{
    for (int ndx = 0; ndx <= UCHAR_MAX; ndx++)
        if (isspace(ndx))
            printf("0x%02x ", ndx);
}

Output:

0x09 0x0a 0x0b 0x0c 0x0d 0x20

References

  • C23 standard (ISO/IEC 9899:2023):
    • 7.4.1.10 The isspace function (p: TBD)
  • C17 standard (ISO/IEC 9899:2018):
    • 7.4.1.10 The isspace function (p: 147)
  • C11 standard (ISO/IEC 9899:2011):
    • 7.4.1.10 The isspace function (p: 202-203)
  • C99 standard (ISO/IEC 9899:1999):
    • 7.4.1.10 The isspace function (p: 183-184)
  • C89/C90 standard (ISO/IEC 9899:1990):
    • 4.3.1.9 The isspace function

See also

(C95)
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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