---
name: "isxdigit"
section: "3"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/isxdigit"
---

# isxdigit(3)

hexadecimal-digit character test

## NAME

**isxdigit,** **ishexnumber** – hexadecimal-digit character test

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

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

*int*\

**isxdigit**(*int c*);

*int*\

**ishexnumber**(*int c*);

## DESCRIPTION

The **isxdigit**() function tests for any hexadecimal-digit character. Regardless of locale, this includes the following characters only:

| |
| --- |
| \`\`0'' \`\`1'' \`\`2'' \`\`3'' \`\`4'' |
| \`\`5'' \`\`6'' \`\`7'' \`\`8'' \`\`9'' |
| \`\`A'' \`\`B'' \`\`C'' \`\`D'' \`\`E'' |
| \`\`F'' \`\`a'' \`\`b'' \`\`c'' \`\`d'' |
| \`\`e'' \`\`f'' |

The **ishexnumber**() function behaves similarly to **isxdigit**(), but may recognize additional characters, depending on the current locale setting.

The value of the argument must be representable as an *unsigned char* or the value of EOF.

## RETURN VALUES

The **isxdigit**() function returns zero if the character tests false and returns 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 **iswxdigit**() function should be used instead.

## SEE ALSO

[ctype(3)](/ctype/3.md), [isalnum\_l(3)](/isalnum_l/3.md), [iswxdigit(3)](/iswxdigit/3.md), [ascii(7)](/ascii/7.md)

## STANDARDS

The **isxdigit**() function conforms to ISO/IEC 9899:1990 (“ISO C90”).

## HISTORY

The **ishexnumber**() function appeared in 4.4BSD.