ISBLANK(3) | Library Functions Manual | ISBLANK(3)

# NAME

`isblank`, `isblank_l` — blank-space single-byte character test

# SYNOPSIS

`#include <ctype.h>`

int
`isblank`(int c);

int
`isblank_l`(int c, locale_t locale);

# DESCRIPTION

The `isblank`() and `isblank_l`() functions test for blank-space characters. In the C locale, the complete list of blank-space characters is:

‘ ’
  Space character.
`\t`
  Horizontal tab.

OpenBSD always uses the C locale for these functions, ignoring the global locale, the thread-specific locale, and the locale argument.

# RETURN VALUES

These functions return zero if the character tests false or non-zero if the character tests true.

# ENVIRONMENT

On systems supporting non-ASCII single-byte character encodings, these functions may return non-zero for additional characters, and the results of `isblank`() may depend on the `LC_CTYPE` locale(1).

# SEE ALSO

isalnum(3), isalpha(3), isascii(3), iscntrl(3), isdigit(3), isgraph(3), islower(3), isprint(3), ispunct(3), isspace(3), isupper(3), iswblank(3), isxdigit(3), stdio(3), toascii(3), tolower(3), toupper(3), ascii(7)

# STANDARDS

The `isblank`() function conforms to ISO/IEC 9899:1999 (“ISO C99”), and `isblank_l`() to IEEE Std 1003.1-2008 (“POSIX.1”).

# HISTORY

The `isblank`() function has been available since 4.4BSD, and `isblank_l`() since OpenBSD 6.2.

# CAVEATS

The argument c must be `EOF` or representable as an unsigned char; otherwise, the result is undefined.

September 11, 2022 | Debian