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ICONV(3) Linux Programmer's Manual ICONV(3)
NAME
iconv - perform character set conversion
SYNOPSIS
#include <iconv.h>
size_t iconv(iconv_t cd,
char **restrict inbuf, size_t *restrict inbytesleft,
char **restrict outbuf, size_t *restrict 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 conver‐
sion. 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 con‐
tained 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 be‐
ginning 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 con‐
versions 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 re‐
turns (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 writ‐
ten. 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 decre‐
ments *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 er‐
ror, iconv() returns (size_t) -1 and sets errno to indicate the error.
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)
GNU 2021-03-22 ICONV(3)