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m4rtin 10-04-2012 06:16 PM
are shell utilities able to detect if the STDOUT is piped
 
I know that shell utilities are able to understand when the output is directed to a file. Fow example ls(1) understands if it is directed to a file and runs "ls -1" in this case:

Code:
HP@potato:~/test$ ls
file.txt  test.txt
HP@potato:~/test$ ls > /tmp/ls.txt
HP@potato:~/test$ cat /tmp/ls.txt
file.txt
test.txt
HP@potato:~/test$
However, is it possible that utility understands if it's piped to other program? For example if I grep the output of iconv(1) it prints out forward slashed for some reason:

Code:
HP@potato:~/test$ iconv -l | grep WINDOWS-1251
WINDOWS-1251//
HP@potato:~/test$
How to explain this? And in general, are utilities able to understand if their STDOUT is used as STDIN to other utilities? Any exaples? :)

ip_address 10-04-2012 08:19 PM
on mac os x

Code:
$ iconv -l | grep WINDOWS

CP1250 MS-EE WINDOWS-1250
CP1251 MS-CYRL WINDOWS-1251
CP1252 MS-ANSI WINDOWS-1252
CP1253 MS-GREEK WINDOWS-1253
CP1254 MS-TURK WINDOWS-1254
CP1255 MS-HEBR WINDOWS-1255
CP1256 MS-ARAB WINDOWS-1256
CP1257 WINBALTRIM WINDOWS-1257
CP1258 WINDOWS-1258
CP874 WINDOWS-874
CP936 MS936 WINDOWS-936
Code:
$ iconv -l | grep WINDOWS > iconv_windows.txt
Code:
$ cat iconv_windows.txt

CP1250 MS-EE WINDOWS-1250
CP1251 MS-CYRL WINDOWS-1251
CP1252 MS-ANSI WINDOWS-1252
CP1253 MS-GREEK WINDOWS-1253
CP1254 MS-TURK WINDOWS-1254
CP1255 MS-HEBR WINDOWS-1255
CP1256 MS-ARAB WINDOWS-1256
CP1257 WINBALTRIM WINDOWS-1257
CP1258 WINDOWS-1258
CP874 WINDOWS-874
CP936 MS936 WINDOWS-936
what's the problem?

firstfire 10-04-2012 11:42 PM
Hi.

Here is how it is done in the tac utility:
Code:
  file_size = lseek (fd, 0, SEEK_END);

  ok = (file_size < 0 || isatty (fd)
        ? tac_nonseekable (fd, filename)
        : tac_seekable (fd, filename));
lseek() returns -1 on error, that is when file descriptor is not seekable (e.g. pipes). isatty() returns 1 when fd refers to a terminal.

EDIT:
Here is relevant chunk from ls.c:
Code:
    case LS_LS:
      /* This is for the `ls' program.  */
      if (isatty (STDOUT_FILENO))
        {
          format = many_per_line;
          /* See description of qmark_funny_chars, above.  */
          qmark_funny_chars = true;
        }
      else
        {
          format = one_per_line;
          qmark_funny_chars = false;
        }
      break;
Quite readable per se I suppose.

bigearsbilly 10-09-2012 03:48 AM
fstat can be used as well and have a look here

http://pubs.opengroup.org/onlinepubs/9699919799/

Reuti 10-10-2012 08:45 AM
Also the file descriptor 1 will tell:
Code:
$ ls /proc/self/fd/1 -lh
lrwx------ 1 reuti xxx 64 Oct 10 15:42 /proc/self/fd/1 -> /dev/pts/1
$ ls /proc/self/fd/1 -lh | cat
l-wx------ 1 reuti xxx 64 Oct 10 15:42 /proc/self/fd/1 -> pipe:[2970598]

m4rtin 10-28-2012 04:23 PM
ip_address,

on latest Debian and OpenSUSE releases(iconv 2.11.3) if I run "iconv -l" without piping it's output to another utility, I see following output:

Code:
martin@potato:~$ iconv -l
The following list contain all the coded character sets known.  This does
not necessarily mean that all combinations of these names can be used for
the FROM and TO command line parameters.  One coded character set can be
listed with several different names (aliases).

  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, BRF, 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, CP803, CP813, CP819, CP850, CP851, CP852, CP855,
  CP856, CP857, CP860, CP861, CP862, CP863, CP864, CP865, CP866, CP866NAV,
  CP868, CP869, CP870, CP871, CP874, CP875, CP880, CP891, CP901, CP902, CP903,
  CP904, CP905, CP912, CP915, CP916, CP918, CP920, CP921, CP922, CP930, CP932,
  CP933, CP935, CP936, CP937, CP939, CP949, CP950, CP1004, CP1008, CP1025,
  CP1026, CP1046, CP1047, CP1070, CP1079, CP1081, CP1084, CP1089, CP1097,
  CP1112, CP1122, CP1123, CP1124, CP1125, CP1129, CP1130, CP1132, CP1133,
  CP1137, CP1140, CP1141, CP1142, CP1143, CP1144, CP1145, CP1146, CP1147,
  CP1148, CP1149, CP1153, CP1154, CP1155, CP1156, CP1157, CP1158, CP1160,
  CP1161, CP1162, CP1163, CP1164, CP1166, CP1167, CP1250, CP1251, CP1252,
  CP1253, CP1254, CP1255, CP1256, CP1257, CP1258, CP1282, CP1361, CP1364,
  CP1371, CP1388, CP1390, CP1399, CP4517, CP4899, CP4909, CP4971, CP5347,
  CP9030, CP9066, CP9448, CP10007, CP12712, CP16804, 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, CSIBM803, CSIBM851, CSIBM855, CSIBM856,
  CSIBM857, CSIBM860, CSIBM863, CSIBM864, CSIBM865, CSIBM866, CSIBM868,
  CSIBM869, CSIBM870, CSIBM871, CSIBM880, CSIBM891, CSIBM901, CSIBM902,
  CSIBM903, CSIBM904, CSIBM905, CSIBM918, CSIBM921, CSIBM922, CSIBM930,
  CSIBM932, CSIBM933, CSIBM935, CSIBM937, CSIBM939, CSIBM943, CSIBM1008,
  CSIBM1025, CSIBM1026, CSIBM1097, CSIBM1112, CSIBM1122, CSIBM1123, CSIBM1124,
  CSIBM1129, CSIBM1130, CSIBM1132, CSIBM1133, CSIBM1137, CSIBM1140, CSIBM1141,
  CSIBM1142, CSIBM1143, CSIBM1144, CSIBM1145, CSIBM1146, CSIBM1147, CSIBM1148,
  CSIBM1149, CSIBM1153, CSIBM1154, CSIBM1155, CSIBM1156, CSIBM1157, CSIBM1158,
  CSIBM1160, CSIBM1161, CSIBM1163, CSIBM1164, CSIBM1166, CSIBM1167, CSIBM1364,
  CSIBM1371, CSIBM1388, CSIBM1390, CSIBM1399, CSIBM4517, CSIBM4899, CSIBM4909,
  CSIBM4971, CSIBM5347, CSIBM9030, CSIBM9066, CSIBM9448, CSIBM12712,
  CSIBM16804, 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, CSWINDOWS31J, 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-MS, EUC-JP, EUC-KR, EUC-TW, EUCCN, EUCJP-MS,
  EUCJP-OPEN, EUCJP-WIN, 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-GREEK8, HP-ROMAN8,
  HP-ROMAN9, HP-THAI8, HP-TURKISH8, HPGREEK8, HPROMAN8, HPROMAN9, HPTHAI8,
  HPTURKISH8, HU, IBM-803, IBM-856, IBM-901, IBM-902, IBM-921, IBM-922,
  IBM-930, IBM-932, IBM-933, IBM-935, IBM-937, IBM-939, IBM-943, IBM-1008,
  IBM-1025, IBM-1046, IBM-1047, IBM-1097, IBM-1112, IBM-1122, IBM-1123,
  IBM-1124, IBM-1129, IBM-1130, IBM-1132, IBM-1133, IBM-1137, IBM-1140,
  IBM-1141, IBM-1142, IBM-1143, IBM-1144, IBM-1145, IBM-1146, IBM-1147,
  IBM-1148, IBM-1149, IBM-1153, IBM-1154, IBM-1155, IBM-1156, IBM-1157,
  IBM-1158, IBM-1160, IBM-1161, IBM-1162, IBM-1163, IBM-1164, IBM-1166,
  IBM-1167, IBM-1364, IBM-1371, IBM-1388, IBM-1390, IBM-1399, IBM-4517,
  IBM-4899, IBM-4909, IBM-4971, IBM-5347, IBM-9030, IBM-9066, IBM-9448,
  IBM-12712, IBM-16804, IBM037, IBM038, IBM256, IBM273, IBM274, IBM275, IBM277,
  IBM278, IBM280, IBM281, IBM284, IBM285, IBM290, IBM297, IBM367, IBM420,
  IBM423, IBM424, IBM437, IBM500, IBM775, IBM803, 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, IBM901, IBM902, IBM903, IBM904, IBM905,
  IBM912, IBM915, IBM916, IBM918, IBM920, IBM921, IBM922, IBM930, IBM932,
  IBM933, IBM935, IBM937, IBM939, IBM943, IBM1004, IBM1008, IBM1025, IBM1026,
  IBM1046, IBM1047, IBM1089, IBM1097, IBM1112, IBM1122, IBM1123, IBM1124,
  IBM1129, IBM1130, IBM1132, IBM1133, IBM1137, IBM1140, IBM1141, IBM1142,
  IBM1143, IBM1144, IBM1145, IBM1146, IBM1147, IBM1148, IBM1149, IBM1153,
  IBM1154, IBM1155, IBM1156, IBM1157, IBM1158, IBM1160, IBM1161, IBM1162,
  IBM1163, IBM1164, IBM1166, IBM1167, IBM1364, IBM1371, IBM1388, IBM1390,
  IBM1399, IBM4517, IBM4899, IBM4909, IBM4971, IBM5347, IBM9030, IBM9066,
  IBM9448, IBM12712, IBM16804, 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-8859-9E, 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, ISO/TR_11548-1,
  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, ISO8859-9E, ISO8859-10, ISO8859-11, ISO8859-13,
  ISO8859-14, ISO8859-15, ISO8859-16, ISO11548-1, ISO88591, ISO88592, ISO88593,
  ISO88594, ISO88595, ISO88596, ISO88597, ISO88598, ISO88599, ISO88599E,
  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_8859-7:2003, ISO_8859-8, ISO_8859-8:1988,
  ISO_8859-9, ISO_8859-9:1989, ISO_8859-9E, ISO_8859-10, ISO_8859-10:1992,
  ISO_8859-14, ISO_8859-14:1998, ISO_8859-15, ISO_8859-15:1998, ISO_8859-16,
  ISO_8859-16:2001, ISO_9036, ISO_10367-BOX, ISO_10367BOX, ISO_11548-1,
  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-RU, KOI8-T, KOI8-U, KOI8, KOI8R, KOI8U, KSC5636, L1, L2, L3, L4, L5, L6,
  L7, L8, L10, LATIN-9, LATIN-GREEK-1, LATIN-GREEK, LATIN1, LATIN2, LATIN3,
  LATIN4, LATIN5, LATIN6, LATIN7, LATIN8, LATIN9, LATIN10, LATINGREEK,
  LATINGREEK1, MAC-CENTRALEUROPE, MAC-CYRILLIC, MAC-IS, MAC-SAMI, MAC-UK, MAC,
  MACCYRILLIC, MACINTOSH, MACIS, MACUK, MACUKRAINIAN, MIK, MS-ANSI, MS-ARAB,
  MS-CYRL, MS-EE, MS-GREEK, MS-HEBR, MS-MAC-CYRILLIC, MS-TURK, MS932, MS936,
  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, OSF10010004,
  OSF10010006, OSF10020025, OSF10020111, OSF10020115, OSF10020116, OSF10020118,
  OSF10020122, OSF10020129, OSF10020352, OSF10020354, OSF10020357, OSF10020359,
  OSF10020360, OSF10020364, OSF10020365, OSF10020366, OSF10020367, OSF10020370,
  OSF10020387, OSF10020388, OSF10020396, OSF10020402, OSF10020417, PT, PT2,
  PT154, R8, R9, RK1048, ROMAN8, ROMAN9, RUSCII, SE, SE2, SEN_850200_B,
  SEN_850200_C, SHIFT-JIS, SHIFT_JIS, SHIFT_JISX0213, SJIS-OPEN, SJIS-WIN,
  SJIS, SS636127, STRK1048-2002, ST_SEV_358-88, T.61-8BIT, T.61, T.618BIT,
  TCVN-5712, TCVN, TCVN5712-1, TCVN5712-1:1993, THAI8, TIS-620, TIS620-0,
  TIS620.2529-1, TIS620.2533-0, TIS620, TS-5881, TSCII, TURKISH8, 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-31J, WINDOWS-874, WINDOWS-936, WINDOWS-1250, WINDOWS-1251,
  WINDOWS-1252, WINDOWS-1253, WINDOWS-1254, WINDOWS-1255, WINDOWS-1256,
  WINDOWS-1257, WINDOWS-1258, WINSAMI2, WS2, YU
martin@potato:~$

Now if I pipe output of "iconv -l" to grep I end up with lines ended with forward-slashes:

Code:
martin@potato:~$ iconv -l | grep WINDOWS
CSWINDOWS31J//
WINDOWS-31J//
WINDOWS-874//
WINDOWS-936//
WINDOWS-1250//
WINDOWS-1251//
WINDOWS-1252//
WINDOWS-1253//
WINDOWS-1254//
WINDOWS-1255//
WINDOWS-1256//
WINDOWS-1257//
WINDOWS-1258//
martin@potato:~$
So "iconv" seems to understand, that it has been piped :)



firstfire,

ok, so using lseek system call utilities can understand whether they are piped or not?



Reuti,

it's difficult to analyze file descriptors under /proc if program finishes almost instantly :P


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