iconv(3)

NAME

   iconv - perform character set conversion

SYNOPSIS

   #include <iconv.h>

   size_t iconv(iconv_t cd,
                char **inbuf, size_t *inbytesleft,
                char **outbuf, size_t *outbytesleft);

DESCRIPTION

   The iconv() function converts a sequence of characters in one character
   encoding to a sequence of characters  in  another  character  encoding.
   The  cd  argument  is  a conversion descriptor, previously created by a
   call to iconv_open(3); the conversion descriptor defines the  character
   encodings  that iconv() uses for the conversion.  The inbuf argument is
   the address of a variable that points to the  first  character  of  the
   input  sequence;  inbytesleft  indicates  the  number  of bytes in that
   buffer.  The outbuf argument is the address of a variable  that  points
   to  the  first  byte  available  in  the  output  buffer;  outbytesleft
   indicates the number of bytes available in the output buffer.

   The main case is when inbuf is not NULL and *inbuf  is  not  NULL.   In
   this  case,  the  iconv()  function  converts  the  multibyte  sequence
   starting at *inbuf to a multibyte sequence  starting  at  *outbuf.   At
   most  *inbytesleft  bytes,  starting  at *inbuf, will be read.  At most
   *outbytesleft bytes, starting at *outbuf, will be written.

   The iconv() function converts one multibyte character at  a  time,  and
   for  each  character  conversion  it  increments  *inbuf and decrements
   *inbytesleft by the number of  converted  input  bytes,  it  increments
   *outbuf  and decrements *outbytesleft by the number of converted output
   bytes, and it updates the conversion state contained  in  cd.   If  the
   character  encoding  of the input is stateful, the iconv() function can
   also convert a sequence of input bytes to an update to  the  conversion
   state  without producing any output bytes; such input is called a shift
   sequence.  The conversion can stop for four reasons:

   1. An invalid multibyte sequence is encountered in the input.  In  this
      case,  it  sets  errno to EILSEQ and returns (size_t) -1.  *inbuf is
      left pointing to the beginning of the invalid multibyte sequence.

   2. The input byte  sequence  has  been  entirely  converted,  that  is,
      *inbytesleft  has gone down to 0.  In this case, iconv() returns the
      number of nonreversible conversions performed during this call.

   3. An incomplete multibyte sequence is encountered in  the  input,  and
      the  input byte sequence terminates after it.  In this case, it sets
      errno to EINVAL and returns (size_t) -1.  *inbuf is left pointing to
      the beginning of the incomplete multibyte sequence.

   4. The output buffer has no more room for the next converted character.
      In this case, it sets errno to E2BIG and returns (size_t) -1.

   A different case is when inbuf is NULL or *inbuf is NULL, but outbuf is
   not  NULL  and *outbuf is not NULL.  In this case, the iconv() function
   attempts to set cd's conversion state to the initial state and store  a
   corresponding  shift sequence at *outbuf.  At most *outbytesleft bytes,
   starting at *outbuf, will be written.  If the output buffer has no more
   room  for  this  reset  sequence,  it  sets  errno to E2BIG and returns
   (size_t) -1.   Otherwise,  it   increments   *outbuf   and   decrements
   *outbytesleft by the number of bytes written.

   A  third  case  is  when inbuf is NULL or *inbuf is NULL, and outbuf is
   NULL or *outbuf is NULL.  In this case, the iconv() function sets  cd's
   conversion state to the initial state.

RETURN VALUE

   The  iconv()  function  returns the number of characters converted in a
   nonreversible way during this  call;  reversible  conversions  are  not
   counted.  In case of error, it sets errno and returns (size_t) -1.

ERRORS

   The following errors can occur, among others:

   E2BIG  There is not sufficient room at *outbuf.

   EILSEQ An invalid multibyte sequence has been encountered in the input.

   EINVAL An  incomplete  multibyte  sequence  has been encountered in the
          input.

VERSIONS

   This function is available in glibc since version 2.1.

ATTRIBUTES

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(7).

   
   Interface  Attribute      Value           
   
   iconv()    Thread safety  MT-Safe race:cd 
   
   The  iconv() function is MT-Safe, as long as callers arrange for mutual
   exclusion on the cd argument.

CONFORMING TO

   POSIX.1-2001, POSIX.1-2008.

NOTES

   In each series of calls to iconv(), the last should be one  with  inbuf
   or  *inbuf equal to NULL, in order to flush out any partially converted
   input.

   Although inbuf and outbuf are typed as char **, this does not mean that
   the  objects they point can be interpreted as C strings or as arrays of
   characters: the interpretation of character byte sequences  is  handled
   internally by the conversion functions.  In some encodings, a zero byte
   may be a valid part of a multibyte character.

   The caller of iconv() must ensure  that  the  pointers  passed  to  the
   function  are  suitable  for  accessing  characters  in the appropriate
   character set.  This includes ensuring correct alignment  on  platforms
   that have tight restrictions on alignment.

SEE ALSO

   iconv_close(3), iconv_open(3), iconvconfig(8)

COLOPHON

   This  page  is  part of release 4.09 of the Linux man-pages project.  A
   description of the project, information about reporting bugs,  and  the
   latest     version     of     this    page,    can    be    found    at
   https://www.kernel.org/doc/man-pages/.

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