1ICONV(3)                   Linux Programmer's Manual                  ICONV(3)
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3
4

NAME

6       iconv - perform character set conversion
7

SYNOPSIS

9       #include <iconv.h>
10
11       size_t iconv(iconv_t cd,
12                    char **restrict inbuf, size_t *restrict inbytesleft,
13                    char **restrict outbuf, size_t *restrict outbytesleft);
14

DESCRIPTION

16       The iconv() function converts a sequence of characters in one character
17       encoding to a sequence of characters  in  another  character  encoding.
18       The  cd  argument  is  a conversion descriptor, previously created by a
19       call to iconv_open(3); the conversion descriptor defines the  character
20       encodings  that iconv() uses for the conversion.  The inbuf argument is
21       the address of a variable that points to the first character of the in‐
22       put sequence; inbytesleft indicates the number of bytes in that buffer.
23       The outbuf argument is the address of a variable  that  points  to  the
24       first  byte  available in the output buffer; outbytesleft indicates the
25       number of bytes available in the output buffer.
26
27       The main case is when inbuf is not NULL and *inbuf  is  not  NULL.   In
28       this  case, the iconv() function converts the multibyte sequence start‐
29       ing at *inbuf to a multibyte sequence starting  at  *outbuf.   At  most
30       *inbytesleft  bytes,  starting  at *inbuf, will be read.  At most *out‐
31       bytesleft bytes, starting at *outbuf, will be written.
32
33       The iconv() function converts one multibyte character at  a  time,  and
34       for  each character conversion it increments *inbuf and decrements *in‐
35       bytesleft by the number of converted input bytes, it increments *outbuf
36       and  decrements  *outbytesleft by the number of converted output bytes,
37       and it updates the conversion state contained in cd.  If the  character
38       encoding  of  the input is stateful, the iconv() function can also con‐
39       vert a sequence of input bytes to an update  to  the  conversion  state
40       without  producing  any  output bytes; such input is called a shift se‐
41       quence.  The conversion can stop for four reasons:
42
43       1. An invalid multibyte sequence is encountered in the input.  In  this
44          case,  it  sets  errno to EILSEQ and returns (size_t) -1.  *inbuf is
45          left pointing to the beginning of the invalid multibyte sequence.
46
47       2. The input byte sequence has been entirely converted, that  is,  *in‐
48          bytesleft  has  gone  down  to 0.  In this case, iconv() returns the
49          number of nonreversible conversions performed during this call.
50
51       3. An incomplete multibyte sequence is encountered in  the  input,  and
52          the  input byte sequence terminates after it.  In this case, it sets
53          errno to EINVAL and returns (size_t) -1.  *inbuf is left pointing to
54          the beginning of the incomplete multibyte sequence.
55
56       4. The output buffer has no more room for the next converted character.
57          In this case, it sets errno to E2BIG and returns (size_t) -1.
58
59       A different case is when inbuf is NULL or *inbuf is NULL, but outbuf is
60       not  NULL  and *outbuf is not NULL.  In this case, the iconv() function
61       attempts to set cd's conversion state to the initial state and store  a
62       corresponding  shift sequence at *outbuf.  At most *outbytesleft bytes,
63       starting at *outbuf, will be written.  If the output buffer has no more
64       room  for  this  reset  sequence,  it  sets  errno to E2BIG and returns
65       (size_t) -1.  Otherwise, it increments  *outbuf  and  decrements  *out‐
66       bytesleft by the number of bytes written.
67
68       A  third  case  is  when inbuf is NULL or *inbuf is NULL, and outbuf is
69       NULL or *outbuf is NULL.  In this case, the iconv() function sets  cd's
70       conversion state to the initial state.
71

RETURN VALUE

73       The  iconv()  function  returns the number of characters converted in a
74       nonreversible way during this  call;  reversible  conversions  are  not
75       counted.   In case of error, iconv() returns (size_t) -1 and sets errno
76       to indicate the error.
77

ERRORS

79       The following errors can occur, among others:
80
81       E2BIG  There is not sufficient room at *outbuf.
82
83       EILSEQ An invalid multibyte sequence has been encountered in the input.
84
85       EINVAL An incomplete multibyte sequence has been encountered in the in‐
86              put.
87

VERSIONS

89       This function is available in glibc since version 2.1.
90

ATTRIBUTES

92       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
93       tributes(7).
94
95       ┌────────────────────────────────────┬───────────────┬─────────────────┐
96Interface                           Attribute     Value           
97       ├────────────────────────────────────┼───────────────┼─────────────────┤
98iconv()                             │ Thread safety │ MT-Safe race:cd │
99       └────────────────────────────────────┴───────────────┴─────────────────┘
100
101       The iconv() function is MT-Safe, as long as callers arrange for  mutual
102       exclusion on the cd argument.
103

CONFORMING TO

105       POSIX.1-2001, POSIX.1-2008.
106

NOTES

108       In  each  series of calls to iconv(), the last should be one with inbuf
109       or *inbuf equal to NULL, in order to flush out any partially  converted
110       input.
111
112       Although inbuf and outbuf are typed as char **, this does not mean that
113       the objects they point can be interpreted as C strings or as arrays  of
114       characters:  the  interpretation of character byte sequences is handled
115       internally by the conversion functions.  In some encodings, a zero byte
116       may be a valid part of a multibyte character.
117
118       The caller of iconv() must ensure that the pointers passed to the func‐
119       tion are suitable for accessing characters in the appropriate character
120       set.   This  includes ensuring correct alignment on platforms that have
121       tight restrictions on alignment.
122

SEE ALSO

124       iconv_close(3), iconv_open(3), iconvconfig(8)
125

COLOPHON

127       This page is part of release 5.12 of the Linux  man-pages  project.   A
128       description  of  the project, information about reporting bugs, and the
129       latest    version    of    this    page,    can     be     found     at
130       https://www.kernel.org/doc/man-pages/.
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134GNU                               2021-03-22                          ICONV(3)
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