---
name: "isspace"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/isspace"
---

# isspace(3)

white-space character test

## NAME

**isspace**, **isspace\_l** – white-space character test

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<ctype.h\>**

*int*\

**isspace**(*int c*);

*int*\

**isspace\_l**(*int c*, *locale\_t loc*);

## DESCRIPTION

The **isspace**() and **isspace\_l**() functions test for white-space characters. For any locale, this includes the following standard characters:

| | | | | | |
| --- | --- | --- | --- | --- | --- |
| \`\`\\t'' | \`\`\\n'' | \`\`\\v'' | \`\`\\f'' | \`\`\\r'' | \`\` '' |

In the "C" locale, **isspace**() and **isspace\_l**() return non-zero for these characters only. The value of the argument must be representable as an *unsigned char* or the value of EOF.

The **isspace\_l**() function takes an explicit locale argument, whereas the **isspace**() function uses the current global or per-thread locale.

## RETURN VALUES

The **isspace**() and **isspace\_l**() functions return zero if the character tests false and return non-zero if the character tests true.

## COMPATIBILITY

The 4.4BSD extension of accepting arguments outside of the range of the *unsigned char* type in locales with large character sets is considered obsolete and may not be supported in future releases. The **iswspace**() or **iswspace\_l**() function should be used instead.

## SEE ALSO

[ctype(3)](/ctype/3.md), [ctype\_l(3)](/ctype_l/3.md), [iswspace(3)](/iswspace/3.md), [iswspace\_l(3)](/iswspace_l/3.md), [multibyte(3)](/multibyte/3.md), [xlocale(3)](/xlocale/3.md), [ascii(7)](/ascii/7.md)

## STANDARDS

The **isspace**() function conforms to ISO/IEC 9899:1990 (“ISO C90”). The **isspace\_l**() function conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

## HISTORY

The **isspace**() function first appeared in Version 7 AT&T UNIX.