---
name: "euc"
section: "5"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd", "macos"]
url: "https://new.carta.tech/euc"
---

# euc(5)

EUC encoding of wide characters

## NAME

**euc** – EUC encoding of wide characters

## SYNOPSIS

**ENCODING** "EUC"

**VARIABLE** *len1* *mask1* *len2* *mask2* *len3* *mask3* *len4* *mask4* *mask*

## DESCRIPTION

**EUC** implements a system of 4 multibyte codesets. A multibyte character in the first codeset consists of *len1* bytes starting with a byte in the range of 0x00 to 0x7f. To allow use of ASCII, *len1* is always 1. A multibyte character in the second codeset consists of *len2* bytes starting with a byte in the range of 0x80-0xff excluding 0x8e and 0x8f. A multibyte character in the third codeset consists of *len3* bytes starting with the byte 0x8e. A multibyte character in the fourth codeset consists of *len4* bytes starting with the byte 0x8f.

The *wchar\_t* encoding of **EUC** multibyte characters is dependent on the *len* and *mask* arguments. First, the bytes are moved into a *wchar\_t* as follows:

```
byte0 << ((lenN-1) * 8) | byte1 << ((lenN-2) * 8) | ... | bytelenN-1
```

The result is then ANDed with *~mask* and ORed with *maskN*. Codesets 2 and 3 are special in that the leading byte (0x8e or 0x8f) is first removed and the *lenN* argument is reduced by 1.

For example, the ja\_JP.eucJP locale has the following *VARIABLE* line:

```
VARIABLE	1 0x0000 2 0x8080 2 0x0080 3 0x8000 0x8080
```

Codeset 1 consists of the values 0x0000 - 0x007f.

Codeset 2 consists of the values who have the bits 0x8080 set.

Codeset 3 consists of the values 0x0080 - 0x00ff.

Codeset 4 consists of the values 0x8000 - 0xff7f excluding the values which have the 0x0080 bit set.

Notice that the global *mask* is set to 0x8080, this implies that from those 2 bits the codeset can be determined.

## SEE ALSO

[localedef(1)](/localedef/1.md), [setlocale(3)](/setlocale/3.md)