# module NKF

`NKF` - Ruby extension for Network Kanji Filter

## Description¶ ↑

This is a Ruby Extension version of nkf (Network Kanji Filter). It converts the first argument and returns converted result. Conversion details are specified by flags as the first argument.

Nkf is a yet another kanji code converter among networks, hosts and terminals. It converts input kanji code to designated kanji code such as ISO-2022-JP, Shift_JIS, EUC-JP, UTF-8 or UTF-16.

One of the most unique faculty of nkf is the guess of the input kanji encodings. It currently recognizes ISO-2022-JP, Shift_JIS, EUC-JP, UTF-8 and UTF-16. So users needn’t set the input kanji code explicitly.

By default, X0201 kana is converted into X0208 kana. For X0201 kana, SO/SI, SSO and ESC-(-I methods are supported. For automatic code detection, nkf assumes no X0201 kana in Shift_JIS. To accept X0201 in Shift_JIS, use -X, -x or -S.

## Flags¶ ↑

### -b -u¶ ↑

Output is buffered (DEFAULT), Output is unbuffered.

### -j -s -e -w -w16 -w32¶ ↑

Output code is ISO-2022-JP (7bit `JIS`), Shift_JIS, EUC-JP, UTF-8N, UTF-16BE, UTF-32BE. Without this option and compile option, ISO-2022-JP is assumed.

### -J -S -E -W -W16 -W32¶ ↑

Input assumption is `JIS` 7 bit, Shift_JIS, EUC-JP, UTF-8, UTF-16, UTF-32.

#### -J¶ ↑

Assume `JIS` input. It also accepts EUC-JP. This is the default. This flag does not exclude Shift_JIS.

#### -S¶ ↑

Assume Shift_JIS and X0201 kana input. It also accepts `JIS`. EUC-JP is recognized as X0201 kana. Without -x flag, X0201 kana (halfwidth kana) is converted into X0208.

#### -E¶ ↑

Assume EUC-JP input. It also accepts `JIS`. Same as -J.

### -t¶ ↑

No conversion.

### -i_¶ ↑

Output sequence to designate JIS-kanji. (DEFAULT B)

### -o_¶ ↑

Output sequence to designate `ASCII`. (DEFAULT B)

### -r¶ ↑

{de/en}crypt ROT13/47

### -h[123] –hiragana –katakana –katakana-hiragana¶ ↑

-h1 –hiragana

  Katakana to Hiragana conversion.

-h2 –katakana

  Hiragana to Katakana conversion.

-h3 –katakana-hiragana

  Katakana to Hiragana and Hiragana to Katakana conversion.

### -T¶ ↑

Text mode output (MS-DOS)

### -l¶ ↑

ISO8859-1 (Latin-1) support

### -f[`m` [- `n`]]¶ ↑

Folding on `m` length with `n` margin in a line. Without this option, fold length is 60 and fold margin is 10.

### -F¶ ↑

New line preserving line folding.

### -Z[0-3]¶ ↑

Convert X0208 alphabet (Fullwidth Alphabets) to `ASCII`.

-Z -Z0

  Convert X0208 alphabet to `ASCII`.

-Z1

  Converts X0208 kankaku to single `ASCII` space.

-Z2

  Converts X0208 kankaku to double `ASCII` spaces.

-Z3

  Replacing Fullwidth >, <, “, & into ‘&gt;’, ‘&lt;’, ‘&quot;’, ‘&amp;’ as in HTML.

### -X -x¶ ↑

Assume X0201 kana in MS-Kanji. With -X or without this option, X0201 is converted into X0208 Kana. With -x, try to preserve X0208 kana and do not convert X0201 kana to X0208. In `JIS` output, ESC-(-I is used. In `EUC` output, SSO is used.

### -B[0-2]¶ ↑

Assume broken JIS-Kanji input, which lost ESC. Useful when your site is using old B-News Nihongo patch.

-B1

  allows any char after ESC-( or ESC-$.

-B2

  forces `ASCII` after NL.

### -I¶ ↑

Replacing non iso-2022-jp char into a geta character (substitute character in Japanese).

### -d -c¶ ↑

Delete r in line feed, Add r in line feed.

### -m[BQN0]¶ ↑

MIME ISO-2022-JP/ISO8859-1 decode. (DEFAULT) To see ISO8859-1 (Latin-1) -l is necessary.

-mB

  Decode MIME base64 encoded stream. Remove header or other part before

conversion.

-mQ

  Decode MIME quoted stream. ‘_’ in quoted stream is converted to space.

-mN

  Non-strict decoding.

It allows line break in the middle of the base64 encoding.

-m0

  No MIME decode.

### -M¶ ↑

MIME encode. Header style. All `ASCII` code and control characters are intact. Kanji conversion is performed before encoding, so this cannot be used as a picture encoder.

-MB

  MIME encode `Base64` stream.

-MQ

  Perform quoted encoding.

### -l¶ ↑

Input and output code is ISO8859-1 (Latin-1) and ISO-2022-JP. -s, -e and -x are not compatible with this option.

### -L[uwm]¶ ↑

new line mode Without this option, nkf doesn’t convert line breaks.

-Lu

  unix (LF)

-Lw

  windows (CRLF)

-Lm

  mac (CR)

### –fj –unix –mac –msdos –windows¶ ↑

convert for these system

### –jis –euc –sjis –mime –base64¶ ↑

convert for named code

### –jis-input –euc-input –sjis-input –mime-input –base64-input¶ ↑

assume input system

### –ic=`input codeset` –oc=`output codeset`¶ ↑

`Set` the input or output codeset. `NKF` supports following codesets and those codeset name are case insensitive.

ISO-2022-JP

  a.k.a. RFC1468, 7bit `JIS`, JUNET

EUC-JP (eucJP-nkf)

  a.k.a. AT&T `JIS`, Japanese `EUC`, UJIS

eucJP-ascii

  a.k.a. x-eucjp-open-19970715-ascii

eucJP-ms

  a.k.a. x-eucjp-open-19970715-ms

CP51932

  Microsoft Version of EUC-JP.

Shift_JIS

  `SJIS`, MS-Kanji

Windows-31J

  a.k.a. CP932

UTF-8

  same as UTF-8N

UTF-8N

  UTF-8 without BOM

UTF-8-BOM

  UTF-8 with BOM

UTF-16

  same as UTF-16BE

UTF-16BE

  UTF-16 Big Endian without BOM

UTF-16BE-BOM

  UTF-16 Big Endian with BOM

UTF-16LE

  UTF-16 Little Endian without BOM

UTF-16LE-BOM

  UTF-16 Little Endian with BOM

UTF-32

  same as UTF-32BE

UTF-32BE

  UTF-32 Big Endian without BOM

UTF-32BE-BOM

  UTF-32 Big Endian with BOM

UTF-32LE

  UTF-32 Little Endian without BOM

UTF-32LE-BOM

  UTF-32 Little Endian with BOM

UTF8-MAC

  NKDed UTF-8, a.k.a. UTF8-NFD (input only)

### –fb-{skip, html, xml, perl, java, subchar}¶ ↑

Specify the way that nkf handles unassigned characters. Without this option, –fb-skip is assumed.

### –prefix= `escape character` `target character` ..¶ ↑

When nkf converts to Shift_JIS, nkf adds a specified escape character to specified 2nd byte of Shift_JIS characters. 1st byte of argument is the escape character and following bytes are target characters.

### –no-cp932ext¶ ↑

Handle the characters extended in CP932 as unassigned characters.

## –no-best-fit-chars¶ ↑

When Unicode to Encoded byte conversion, don’t convert characters which is not round trip safe. When Unicode to Unicode conversion, with this and -x option, nkf can be used as UTF converter. (In other words, without this and -x option, nkf doesn’t save some characters)

When nkf convert string which related to path, you should use this option.

### –cap-input¶ ↑

Decode hex encoded characters.

### –url-input¶ ↑

Unescape percent escaped characters.

### –¶ ↑

Ignore rest of -option.

### Constants

ASCII
AUTO
BINARY
EUC
GEM_VERSION

  Version of nkf library

JIS
NKF_RELEASE_DATE

  Release date of nkf

NKF_VERSION

  Version of nkf

NOCONV
SJIS
UNKNOWN
UTF16
UTF32
UTF8
VERSION

  Full version string of nkf

### Public Class Methods

guess(str) → encoding click to toggle source

Returns guessed encoding of str by nkf routine.

    static VALUE
    rb_nkf_guess(VALUE obj, VALUE src)
    {
        reinit();

        input_ctr = 0;
        input = (unsigned char *)StringValuePtr(src);
        i_len = RSTRING_LENINT(src);

        guess_f = TRUE;
        kanji_convert( NULL );
        guess_f = FALSE;

        return rb_enc_from_encoding(rb_nkf_enc_get(get_guessed_code()));
    }

nkf(opt, str) → string click to toggle source

Convert str and return converted result. Conversion details are specified by opt as `String`.

    require 'nkf'
    output = NKF.nkf("-s", input)

    static VALUE
    rb_nkf_convert(VALUE obj, VALUE opt, VALUE src)
    {
        VALUE tmp;
        reinit();
        nkf_split_options(StringValueCStr(opt));
        if (!output_encoding) rb_raise(rb_eArgError, "no output encoding given");

        switch (nkf_enc_to_index(output_encoding)) {
        case UTF_8_BOM:    output_encoding = nkf_enc_from_index(UTF_8); break;
        case UTF_16BE_BOM: output_encoding = nkf_enc_from_index(UTF_16BE); break;
        case UTF_16LE_BOM: output_encoding = nkf_enc_from_index(UTF_16LE); break;
        case UTF_32BE_BOM: output_encoding = nkf_enc_from_index(UTF_32BE); break;
        case UTF_32LE_BOM: output_encoding = nkf_enc_from_index(UTF_32LE); break;
        }
        output_bom_f = FALSE;

        incsize = INCSIZE;

        input_ctr = 0;
        input = (unsigned char *)StringValuePtr(src);
        i_len = RSTRING_LENINT(src);
        tmp = rb_str_new(0, i_len*3 + 10);

        output_ctr = 0;
        output     = (unsigned char *)RSTRING_PTR(tmp);
        o_len      = RSTRING_LENINT(tmp);
        *output    = '\0';

        /* use _result_ begin*/
        result = tmp;
        kanji_convert(NULL);
        result = Qnil;
        /* use _result_ end */

        rb_str_set_len(tmp, output_ctr);

        if (mimeout_f)
            rb_enc_associate(tmp, rb_usascii_encoding());
        else
            rb_enc_associate(tmp, rb_nkf_enc_get(nkf_enc_name(output_encoding)));

        return tmp;
    }