iconv - perform character set conversion
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:
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.
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.
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.
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.
The following errors can occur, among others:
There is not sufficient room at *outbuf
.
An invalid multibyte sequence has been encountered in the input.
An incomplete multibyte sequence has been encountered in the input.
This function is available in glibc since version 2.1.
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.
POSIX.1-2001, POSIX.1-2008.
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.
iconv_close(3), iconv_open(3), iconvconfig(8)
This page is part of release 4.15 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/.