簡介
頭檔案"iconv.h"。iconv命令可以將一種已知的字元集檔案轉換成另一種已知的字元集檔案。它的作用是在多種國際編碼格式之間進行文本內碼的轉換。
linux下的函式原型
size_t iconv(iconv_t cd, char **inbuf, size_t *inbytesleft, char **outbuf, size_t *outbytesleft);
主要內容
iconv是一個電腦程式以及一套應用程式編程接口的名稱。作為應用程式的iconv採用命令行界面，允許將某種特定編碼的檔案轉換為另一種編碼。
iconv基於GPL公開原始碼，是GNU項目的一部分。在各種UNIX作業系統下均可使用，而在Windows系統，需要特殊的環境如cygwin或者GnuWin32等軟體平台下方可使用。現在在SourceForge上也有運行於Windows系統的，需要同時安裝gettext程式。
目前版本為2.3.26，支持的內碼包括：Unicode相關編碼，如UTF-8、UTF-16等等，各國採用的ANSI編碼，其中包括GB2312、BIG5等中文編碼方式。
作為編程接口的iconv包括3個函式：
iconv_open函式用於初始化用於轉換的內部緩衝區，需要指明需要從何種編碼方式轉換到哪一種。
iconv函式進行實際的轉換，需要給出兩個間接緩衝區指針和剩餘位元組數指針。該函式需要更新所有相關信息，因此將不可改寫的指針傳遞給iconv是錯誤的。
iconv_close函式釋放iconv_open函式的緩衝區。
linux下使用方法
舉例
例如：從GB2312轉換為UTF-8。用法：iconv [選項...] [檔案...]
Convert encoding of given files from one encoding to another.
輸入/輸出格式規範：
-f，--from-code=NAME 始文本編碼
-t, --to-code=NAME 輸出編碼
信息：
-l, --list 列舉所有已知的字元集
輸出控制：
-c 從輸出中忽略無效的字元
-o, --output=FILE 輸出檔案
-s, --silent suppress warnings
--verbose 列印進度信息
-?, --help 給出該系統求助列表
--usage 給出簡要的用法信息
-V, --version 列印程式版本號
Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.
類似命令: piconv , convmv
piconv是流模式的,處理超大檔案比較方便. convmv是給檔案名稱重命名的,windows和linux系統間切換後尤其有用
所有已知的字元集
437, 500, 500V1, 850, 851, 852, 855, 856, 857, 860, 861, 862, 863, 864, 865,866, 866NAV, 869, 874, 904, 1026, 1046, 1047, 8859_1, 8859_2, 8859_3, 8859_4,
8859_5, 8859_6, 8859_7, 8859_8, 8859_9, 10646-1:1993, 10646-1:1993/UCS4,
ANSI_X3.4-1968, ANSI_X3.4-1986, ANSI_X3.4, ANSI_X3.110-1983, ANSI_X3.110,
ARABIC, ARABIC7, ARMSCII-8, ASCII, ASMO-708, ASMO_449, BALTIC, BIG-5,
BIG-FIVE, BIG5-HKSCS, BIG5, BIG5HKSCS, BIGFIVE, BS_4730, CA, CN-BIG5, CN-GB,
CN, CP-AR, CP-GR, CP-HU, CP037, CP038, CP273, CP274, CP275, CP278, CP280,
CP281, CP282, CP284, CP285, CP290, CP297, CP367, CP420, CP423, CP424, CP437,
CP500, CP737, CP775, CP813, CP819, CP850, CP851, CP852, CP855, CP856, CP857,
CP860, CP861, CP862, CP863, CP864, CP865, CP866, CP866NAV, CP868, CP869,
CP870, CP871, CP874, CP875, CP880, CP891, CP903, CP904, CP905, CP912, CP915,
CP916, CP918, CP920, CP922, CP930, CP932, CP933, CP935, CP936, CP937, CP939,
CP949, CP950, CP1004, CP1026, CP1046, CP1047, CP1070, CP1079, CP1081, CP1084,
CP1089, CP1124, CP1125, CP1129, CP1132, CP1133, CP1160, CP1161, CP1162,
CP1163, CP1164, CP1250, CP1251, CP1252, CP1253, CP1254, CP1255, CP1256,
CP1257, CP1258, CP1361, CP10007, CPIBM861, CSA7-1, CSA7-2, CSASCII,
CSA_T500-1983, CSA_T500, CSA_Z243.4-1985-1, CSA_Z243.4-1985-2,
CSA_Z243.419851, CSA_Z243.419852, CSDECMCS, CSEBCDICATDE, CSEBCDICATDEA,
CSEBCDICCAFR, CSEBCDICDKNO, CSEBCDICDKNOA, CSEBCDICES, CSEBCDICESA,
CSEBCDICESS, CSEBCDICFISE, CSEBCDICFISEA, CSEBCDICFR, CSEBCDICIT, CSEBCDICPT,
CSEBCDICUK, CSEBCDICUS, CSEUCKR, CSEUCPKDFMTJAPANESE, CSGB2312, CSHPROMAN8,
CSIBM037, CSIBM038, CSIBM273, CSIBM274, CSIBM275, CSIBM277, CSIBM278,
CSIBM280, CSIBM281, CSIBM284, CSIBM285, CSIBM290, CSIBM297, CSIBM420,
CSIBM423, CSIBM424, CSIBM500, CSIBM851, CSIBM855, CSIBM856, CSIBM857,
CSIBM860, CSIBM863, CSIBM864, CSIBM865, CSIBM866, CSIBM868, CSIBM869,
CSIBM870, CSIBM871, CSIBM880, CSIBM891, CSIBM903, CSIBM904, CSIBM905,
CSIBM918, CSIBM922, CSIBM930, CSIBM932, CSIBM933, CSIBM935, CSIBM937,
CSIBM939, CSIBM943, CSIBM1026, CSIBM1124, CSIBM1129, CSIBM1132, CSIBM1133,
CSIBM1160, CSIBM1161, CSIBM1163, CSIBM1164, CSIBM11621162,
CSISO4UNITEDKINGDOM, CSISO10SWEDISH, CSISO11SWEDISHFORNAMES,
CSISO14JISC6220RO, CSISO15ITALIAN, CSISO16PORTUGESE, CSISO17SPANISH,
CSISO18GREEK7OLD, CSISO19LATINGREEK, CSISO21GERMAN, CSISO25FRENCH,
CSISO27LATINGREEK1, CSISO49INIS, CSISO50INIS8, CSISO51INISCYRILLIC,
CSISO58GB1988, CSISO60DANISHNORWEGIAN, CSISO60NORWEGIAN1, CSISO61NORWEGIAN2,
CSISO69FRENCH, CSISO84PORTUGUESE2, CSISO85SPANISH2, CSISO86HUNGARIAN,
CSISO88GREEK7, CSISO89ASMO449, CSISO90, CSISO92JISC62991984B, CSISO99NAPLPS,
CSISO103T618BIT, CSISO111ECMACYRILLIC, CSISO121CANADIAN1, CSISO122CANADIAN2,
CSISO139CSN369103, CSISO141JUSIB1002, CSISO143IECP271, CSISO150,
CSISO150GREEKCCITT, CSISO151CUBA, CSISO153GOST1976874, CSISO646DANISH,
CSISO2022CN, CSISO2022JP, CSISO2022JP2, CSISO2022KR, CSISO2033,
CSISO5427CYRILLIC, CSISO5427CYRILLIC1981, CSISO5428GREEK, CSISO10367BOX,
CSISOlatin1, CSISOLATIN2, CSISOLATIN3, CSISOLATIN4, CSISOLATIN5, CSISOLATIN6,
CSISOLATINARABIC, CSISOLATINCYRILLIC, CSISOLATINGREEK, CSISOLATINHEBREW,
CSKOI8R, CSKSC5636, CSMACINTOSH, CSNATSDANO, CSNATSSEFI, CSN_369103,
CSPC8CODEPAGE437, CSPC775BALTIC, CSPC850MULTILINGUAL, CSPC862LATINHEBREW,
CSPCP852, CSSHIFTJIS, CSUCS4, CSUNICODE, CUBA, CWI-2, CWI, CYRILLIC, DE,
DEC-MCS, DEC, DECMCS, DIN_66003, DK, DS2089, DS_2089, E13B, EBCDIC-AT-DE-A,
EBCDIC-AT-DE, EBCDIC-BE, EBCDIC-BR, EBCDIC-CA-FR, EBCDIC-CP-AR1,
EBCDIC-CP-AR2, EBCDIC-CP-BE, EBCDIC-CP-CA, EBCDIC-CP-CH, EBCDIC-CP-DK,
EBCDIC-CP-ES, EBCDIC-CP-FI, EBCDIC-CP-FR, EBCDIC-CP-GB, EBCDIC-CP-GR,
EBCDIC-CP-HE, EBCDIC-CP-IS, EBCDIC-CP-IT, EBCDIC-CP-NL, EBCDIC-CP-NO,
EBCDIC-CP-ROECE, EBCDIC-CP-SE, EBCDIC-CP-TR, EBCDIC-CP-US, EBCDIC-CP-WT,
EBCDIC-CP-YU, EBCDIC-CYRILLIC, EBCDIC-DK-NO-A, EBCDIC-DK-NO, EBCDIC-ES-A,
EBCDIC-ES-S, EBCDIC-ES, EBCDIC-FI-SE-A, EBCDIC-FI-SE, EBCDIC-FR,
EBCDIC-GREEK, EBCDIC-INT, EBCDIC-INT1, EBCDIC-IS-FRISS, EBCDIC-IT,
EBCDIC-JP-E, EBCDIC-JP-KANA, EBCDIC-PT, EBCDIC-UK, EBCDIC-US, EBCDICATDE,
EBCDICATDEA, EBCDICCAFR, EBCDICDKNO, EBCDICDKNOA, EBCDICES, EBCDICESA,
EBCDICESS, EBCDICFISE, EBCDICFISEA, EBCDICFR, EBCDICISFRISS, EBCDICIT,
EBCDICPT, EBCDICUK, EBCDICUS, ECMA-114, ECMA-118, ECMA-128, ECMA-CYRILLIC,
ECMACYRILLIC, ELOT_928, ES, ES2, EUC-CN, EUC-JISX0213, EUC-JP, EUC-KR,
EUC-TW, EUCCN, EUCJP, EUCKR, EUCTW, FI, FR, GB, GB2312, GB13000, GB18030,
GBK, GB_1988-80, GB_198880, GEORGIAN-ACADEMY, GEORGIAN-PS, GOST_19768-74,
GOST_19768, GOST_1976874, GREEK-CCITT, GREEK, GREEK7-OLD, GREEK7, GREEK7OLD,
GREEK8, GREEKCCITT, HEBREW, HP-ROMAN8, HPROMAN8, HU, IBM-856, IBM-922,
IBM-930, IBM-932, IBM-933, IBM-935, IBM-937, IBM-939, IBM-943, IBM-1046,
IBM-1124, IBM-1129, IBM-1132, IBM-1133, IBM-1160, IBM-1161, IBM-1162,
IBM-1163, IBM-1164, IBM037, IBM038, IBM256, IBM273, IBM274, IBM275, IBM277,
IBM278, IBM280, IBM281, IBM284, IBM285, IBM290, IBM297, IBM367, IBM420,
IBM423, IBM424, IBM437, IBM500, IBM775, IBM813, IBM819, IBM848, IBM850,
IBM851, IBM852, IBM855, IBM856, IBM857, IBM860, IBM861, IBM862, IBM863,
IBM864, IBM865, IBM866, IBM866NAV, IBM868, IBM869, IBM870, IBM871, IBM874,
IBM875, IBM880, IBM891, IBM903, IBM904, IBM905, IBM912, IBM915, IBM916,
IBM918, IBM920, IBM922, IBM930, IBM932, IBM933, IBM935, IBM937, IBM939,
IBM943, IBM1004, IBM1026, IBM1046, IBM1047, IBM1089, IBM1124, IBM1129,
IBM1132, IBM1133, IBM1160, IBM1161, IBM1162, IBM1163, IBM1164, IEC_P27-1,
IEC_P271, INIS-8, INIS-CYRILLIC, INIS, INIS8, INISCYRILLIC, ISIRI-3342,
ISIRI3342, ISO-2022-CN-EXT, ISO-2022-CN, ISO-2022-JP-2, ISO-2022-JP-3,
ISO-2022-JP, ISO-2022-KR, ISO-8859-1, ISO-8859-2, ISO-8859-3, ISO-8859-4,
ISO-8859-5, ISO-8859-6, ISO-8859-7, ISO-8859-8, ISO-8859-9, ISO-8859-10,
ISO-8859-11, ISO-8859-13, ISO-8859-14, ISO-8859-15, ISO-8859-16, ISO-10646,
ISO-10646/UCS2, ISO-10646/UCS4, ISO-10646/UTF-8, ISO-10646/UTF8, ISO-CELTIC,
ISO-IR-4, ISO-IR-6, ISO-IR-8-1, ISO-IR-9-1, ISO-IR-10, ISO-IR-11, ISO-IR-14,
ISO-IR-15, ISO-IR-16, ISO-IR-17, ISO-IR-18, ISO-IR-19, ISO-IR-21, ISO-IR-25,
ISO-IR-27, ISO-IR-37, ISO-IR-49, ISO-IR-50, ISO-IR-51, ISO-IR-54, ISO-IR-55,
ISO-IR-57, ISO-IR-60, ISO-IR-61, ISO-IR-69, ISO-IR-84, ISO-IR-85, ISO-IR-86,
ISO-IR-88, ISO-IR-89, ISO-IR-90, ISO-IR-92, ISO-IR-98, ISO-IR-99, ISO-IR-100,
ISO-IR-101, ISO-IR-103, ISO-IR-109, ISO-IR-110, ISO-IR-111, ISO-IR-121,
ISO-IR-122, ISO-IR-126, ISO-IR-127, ISO-IR-138, ISO-IR-139, ISO-IR-141,
ISO-IR-143, ISO-IR-144, ISO-IR-148, ISO-IR-150, ISO-IR-151, ISO-IR-153,
ISO-IR-155, ISO-IR-156, ISO-IR-157, ISO-IR-166, ISO-IR-179, ISO-IR-193,
ISO-IR-197, ISO-IR-199, ISO-IR-203, ISO-IR-209, ISO-IR-226, ISO646-CA,
ISO646-CA2, ISO646-CN, ISO646-CU, ISO646-DE, ISO646-DK, ISO646-ES,
ISO646-ES2, ISO646-FI, ISO646-FR, ISO646-FR1, ISO646-GB, ISO646-HU,
ISO646-IT, ISO646-JP-OCR-B, ISO646-JP, ISO646-KR, ISO646-NO, ISO646-NO2,
ISO646-PT, ISO646-PT2, ISO646-SE, ISO646-SE2, ISO646-US, ISO646-YU,
ISO2022CN, ISO2022CNEXT, ISO2022JP, ISO2022JP2, ISO2022KR, ISO6937,
ISO8859-1, ISO8859-2, ISO8859-3, ISO8859-4, ISO8859-5, ISO8859-6, ISO8859-7,
ISO8859-8, ISO8859-9, ISO8859-10, ISO8859-11, ISO8859-13, ISO8859-14,
ISO8859-15, ISO8859-16, ISO88591, ISO88592, ISO88593, ISO88594, ISO88595,
ISO88596, ISO88597, ISO88598, ISO88599, ISO885910, ISO885911, ISO885913,
ISO885914, ISO885915, ISO885916, ISO_646.IRV:1991, ISO_2033-1983, ISO_2033,
ISO_5427-EXT, ISO_5427, ISO_5427:1981, ISO_5427EXT, ISO_5428, ISO_5428:1980,
ISO_6937-2, ISO_6937-2:1983, ISO_6937, ISO_6937:1992, ISO_8859-1,
ISO_8859-1:1987, ISO_8859-2, ISO_8859-2:1987, ISO_8859-3, ISO_8859-3:1988,
ISO_8859-4, ISO_8859-4:1988, ISO_8859-5, ISO_8859-5:1988, ISO_8859-6,
ISO_8859-6:1987, ISO_8859-7, ISO_8859-7:1987, ISO_8859-8, ISO_8859-8:1988,
ISO_8859-9, ISO_8859-9:1989, ISO_8859-10,ISO_8859-10:1992, ISO_8859-14,
ISO_8859-14:1998, ISO_8859-15:1998, ISO_9036, ISO_10367-BOX, ISO_10367BOX,
ISO_69372, IT, JIS_C6220-1969-RO, JIS_C6229-1984-B, JIS_C62201969RO,
JIS_C62291984B, JOHAB, JP-OCR-B, JP, JS, JUS_I.B1.002, KOI-7, KOI-8, KOI8-R,
KOI8-T, KOI8-U, KOI8, KOI8R, KOI8U, KSC5636, L1, L2, L3, L4, L5, L6, L7, L8,
L10, LATIN-GREEK-1, LATIN-GREEK, LATIN1, LATIN2, LATIN3, LATIN4, LATIN5,
LATIN6, LATIN7, LATIN8, LATIN10, LATINGREEK, LATINGREEK1, MAC-CYRILLIC,
MAC-IS, MAC-SAMI, MAC-UK, MAC, MACCYRILLIC, MACINTOSH, MACIS, MACUK,
MACUKRAINIAN, MS-ANSI, MS-ARAB, MS-CYRL, MS-EE, MS-GREEK, MS-HEBR,
MS-MAC-CYRILLIC, MS-TURK, MSCP949, MSCP1361, MSMACCYRILLIC, MSZ_7795.3,
MS_KANJI, NAPLPS, NATS-DANO, NATS-SEFI, NATSDANO, NATSSEFI, NC_NC0010,
NC_NC00-10, NC_NC00-10:81, NF_Z_62-010, NF_Z_62-010_(1973), NF_Z_62-010_1973,
NF_Z_62010, NF_Z_62010_1973, NO, NO2, NS_4551-1, NS_4551-2, NS_45511,
NS_45512, OS2LATIN1, OSF00010001, OSF00010002, OSF00010003, OSF00010004,
OSF00010005, OSF00010006, OSF00010007, OSF00010008, OSF00010009, OSF0001000A,
OSF00010020, OSF00010100, OSF00010101, OSF00010102, OSF00010104, OSF00010105,
OSF00010106, OSF00030010, OSF0004000A, OSF0005000A, OSF05010001, OSF100201A4,
OSF100201A8, OSF100201B5, OSF100201F4, OSF100203B5, OSF1002011C, OSF1002011D,
OSF1002035D, OSF1002035E, OSF1002035F, OSF1002036B, OSF1002037B, OSF10010001,
OSF10020025, OSF10020111, OSF10020115, OSF10020116, OSF10020118, OSF10020122,
OSF10020129, OSF10020352, OSF10020354, OSF10020357, OSF10020359, OSF10020360,
OSF10020364, OSF10020365, OSF10020366, OSF10020367, OSF10020370, OSF10020387,
OSF10020388, OSF10020396, OSF10020402, OSF10020417, PT, PT2, R8, ROMAN8,
RUSCII, SE, SE2, SEN_850200_B, SEN_850200_C, SHIFT-JIS, SHIFT_JIS,
SHIFT_JISX0213, SJIS, SS636127, ST_SEV_358-88, T.61-8BIT, T.61, T.618BIT,
TCVN-5712, TCVN, TCVN5712-1, TCVN5712-1:1993, TIS-620, TIS620-0,
TIS620.2529-1, TIS620.2533-0, TIS620, TS-5881, TSCII, UCS-2, UCS-2BE,
UCS-2LE, UCS-4, UCS-4BE, UCS-4LE, UCS2, UCS4, UHC, UJIS, UK, UNICODE,
UNICODEBIG, UNICODELITTLE, US-ASCII, US, UTF-7, UTF-8, UTF-16, UTF-16BE,
UTF-16LE, UTF-32, UTF-32BE, UTF-32LE, UTF7, UTF8, UTF16, UTF16BE, UTF16LE,
UTF32, UTF32BE, UTF32LE, VISCII, WCHAR_T, WIN-SAMI-2, WINBALTRIM,
WINDOWS-1250, WINDOWS-1251, WINDOWS-1252, WINDOWS-1253, WINDOWS-1254,
WINDOWS-1255, WINDOWS-1256, WINDOWS-1257, WINDOWS-1258, WINSAMI2, WS2, YU
指令：
#iconv -f gb2312 -t utf8 gb1.txt > gb2.txt 將gb1里的編碼從GB2312轉化成UTF-8 並重定向到gb2.txt
除了iconv命令，我們在linux系統下的man page的第三節還可以看到一組iconv函式。它們分別是
iconv_t iconv_open(const char *tocode, const char *fromcode);
size_ticonv(iconv_t cd, char **inbuf, size_t *inbytesleft, char **outbuf, size_t *outbytesleft);
int iconv_close(iconv_t cd);
iconv_open函式用來打開一個編碼轉換的流，iconv函式的作用是實際進行轉換，iconv_close函式的作用就是關閉這個流。實際用法參見下面的例子，下面是一個將UTF-8碼轉換成GBK碼的例子，我們假設已經有了一個uft8編碼的輸入緩衝區inbuf以及這個緩衝區的長度inlen。
iconv_t cd = iconv_open( "GBK", "UTF-8");
char *outbuf = (char *)malloc(inlen * 4 );
bzero( outbuf, inlen * 4);
char *in = inbuf;
char *out = outbuf;
size_t outlen = inlen *4;
iconv（cd, ∈, (size_t *)∈len, &out,&outlen）;
outlen = strlen(outbuf);
printf("%s\n",outbuf);
free(outbuf);
iconv_close(cd);
非常值得注意的地方是：iconv函式會修改參數in和參數out指針所指向的地方，也就是說，在調用iconv函式之前，我們的in和inbuf指針以及out和outbuf指針指向的是同一塊記憶體區域，但是調用之後out指針所指向的地方就不是outbuf了，同理in指針。所以要
char *in = inbuf;
char *out = outbuf;
另外儲存一下，使用或者釋放記憶體的時候也要使用原先的那個指針outbuf和inbuf。
php下使用方法
unix下安裝PHP的module，需要重新編譯PHP，Windows下安裝模板，只需將php.ini里的配置打開相應的dll就可，例如，需要加入gb庫的支持，需要如下設定：extension_dir = “C:/ipaddr/php/extensions/”
(注意，建議寫全地址，並且後面加上/，很多時候是因為這裡設定不對，才導致無法載入其它模組的dll的)
再打開
extension=php_gd2.dll
但如果是安裝iconv.dll，按上面方法，打開php_iconv.dll後，還是無法開啟iconv模組，需要如下配置：
a.上iconv的官方下載站點
下面Windows版的iconv檔案：libiconv-1.9.1.bin.woe32.zip
將這檔案解壓，將bin/下面的charset.dll，iconv.dll，iconv.exe拷貝到c:/windows/ (或其它的系統PATH中)
(ipaddr提醒你，這步是必須的，php_iconv.dll也是調用GNU的iconv庫的，所以，先要安裝GNU的iconv庫)
b.開啟php.ini裡面的php_iconv.dll
c.重啟Apache，再在phpinfo();檢測是否開啟iconv。
最近在做一個程式，需要用到iconv函式把抓取來過的utf-8編碼的頁面轉成gb2312， 發現只有用iconv函式把抓取過來的數據一轉碼數據就會無緣無故的少一些。 讓我鬱悶了好一會兒，去網上一查資料才知道這是iconv函式的一個bug。iconv在轉換字元”—”到gb2312時會出錯
解決方法很簡單，就是在需要轉成的編碼後加 “//IGNORE” 也就是iconv函式第二個參數後.如下：
以下為引用的內容：
iconv(“UTF-8″,”GB2312//IGNORE”,$data)
ignore的意思是忽略轉換時的錯誤，如果沒有ignore參數，所有該字元後面的字元串都無法被保存。
這個iconv()這個函式,在php5中是內置的.
列子
