isblank

C

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Program utilities

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Dynamic memory management

Date and time utilities

Strings library

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Atomic operations (C11)

Thread support (C11)

Technical Specifications

Strings library

Byte strings

Multibyte strings

Wide strings

Null-terminated byte strings

Functions
Character manipulation
isalnum isalpha islower isupper isdigit isxdigit isblank (C99)	iscntrl isgraph isspace isprint ispunct tolower toupper
Conversions to numeric formats
atof atoiatolatoll (C99) strtolstrtoll (C99)	strtoulstrtoull (C99) strtofstrtodstrtold (C99)(C99) strtoimaxstrtoumax (C99)(C99)
String manipulation
strcpystrcpy_s (C11)
strncpystrncpy_s (C11)
strcatstrcat_s (C11)
strncatstrncat_s (C11)
strxfrm
String examination
strlenstrnlen_s (C11) strcmp strncmp strcoll strchr strrchr	strspn strcspn strpbrk strstr strtokstrtok_s (C11)
Memory manipulation
memchr
memcmp
memsetmemset_s (C11)
memcpymemcpy_s (C11)
memmovememmove_s (C11)
Miscellaneous
strerrorstrerror_sstrerrorlen_s (C11)(C11)

Defined in header <ctype.h>
int isblank( int ch );		(since C99)

Checks if the given character is a blank character in the current C locale. In the default C locale, only space (0x20) and horizontal tab (0x09) are classified as blank.

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 blank character, zero otherwise.

Example

Run this code

#include <stdio.h>
#include <ctype.h>
#include <limits.h>

int main(void)
{
    for (int ndx=0; ndx<=UCHAR_MAX; ndx++)
        if (isblank(ndx)) printf("0x%02x\n", ndx);
}

Output:

0x09
0x20

References

• C11 standard (ISO/IEC 9899:2011):

• 7.4.1.3 The isblank function (p: 201)

• C99 standard (ISO/IEC 9899:1999):

• 7.4.1.3 The isblank function (p: 182)

• C89/C90 standard (ISO/IEC 9899:1990):

See also

iswblank (C99)

checks if a wide character is a blank character (function)

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
08	\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
1013	\xA\xD	\12\15	whitespaces (\n, \v, \f, \r)	0	0	0	0	0	0	0	0	0	0	0	0
1431	\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
3347	\x21\x2F	\41\57	!"#$%&'()*+,-./	0	0	0	0	0	0	0	0	0	0	0	0
4857	\x30\x39	\60\71	0123456789	0	0	0	0	0	0	0	0	0	0	0	0
5864	\x3A\x40	\72\100	:;<=>?@	0	0	0	0	0	0	0	0	0	0	0	0
6570	\x41\x46	\101\106	ABCDEF	0	0	0	0	0	0	0	0	0	0	0	0
7190	\x47\x5A	\107\132	GHIJKLMNOP QRSTUVWXYZ	0	0	0	0	0	0	0	0	0	0	0	0
9196	\x5B\x60	\133\140	[\]^_`	0	0	0	0	0	0	0	0	0	0	0	0
97102	\x61\x66	\141\146	abcdef	0	0	0	0	0	0	0	0	0	0	0	0
103122	\x67\x7A	\147\172	ghijklmnop qrstuvwxyz	0	0	0	0	0	0	0	0	0	0	0	0
123126	\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