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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
iconv — codeset conversion function
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 shall convert the sequence of characters from one codeset, in the array specified by
inbuf, into a sequence of corresponding characters in another codeset, in the array specified by outbuf.
The codesets are those specified in the iconv_open() call that returned the conversion descriptor, cd.
The inbuf argument points to a variable that points to the first character in the input buffer and
inbytesleft indicates the number of bytes to the end of the buffer to be converted. The outbuf argument
points to a variable that points to the first available byte in the output buffer and outbytesleft
indicates the number of the available bytes to the end of the buffer.
For state-dependent encodings, the conversion descriptor cd is placed into its initial shift state by a
call for which inbuf is a null pointer, or for which inbuf points to a null pointer. When iconv() is
called in this way, and if outbuf is not a null pointer or a pointer to a null pointer, and outbytesleft
points to a positive value, iconv() shall place, into the output buffer, the byte sequence to change the
output buffer to its initial shift state. If the output buffer is not large enough to hold the entire
reset sequence, iconv() shall fail and set errno to [E2BIG]. Subsequent calls with inbuf as other than a
null pointer or a pointer to a null pointer cause the conversion to take place from the current state of
the conversion descriptor.
If a sequence of input bytes does not form a valid character in the specified codeset, conversion shall
stop after the previous successfully converted character. If the input buffer ends with an incomplete
character or shift sequence, conversion shall stop after the previous successfully converted bytes. If
the output buffer is not large enough to hold the entire converted input, conversion shall stop just
prior to the input bytes that would cause the output buffer to overflow. The variable pointed to by inbuf
shall be updated to point to the byte following the last byte successfully used in the conversion. The
value pointed to by inbytesleft shall be decremented to reflect the number of bytes still not converted
in the input buffer. The variable pointed to by outbuf shall be updated to point to the byte following
the last byte of converted output data. The value pointed to by outbytesleft shall be decremented to
reflect the number of bytes still available in the output buffer. For state-dependent encodings, the
conversion descriptor shall be updated to reflect the shift state in effect at the end of the last
successfully converted byte sequence.
If iconv() encounters a character in the input buffer that is valid, but for which an identical character
does not exist in the target codeset, iconv() shall perform an implementation-defined conversion on this
character.
RETURN VALUE
The iconv() function shall update the variables pointed to by the arguments to reflect the extent of the
conversion and return the number of non-identical conversions performed. If the entire string in the
input buffer is converted, the value pointed to by inbytesleft shall be 0. If the input conversion is
stopped due to any conditions mentioned above, the value pointed to by inbytesleft shall be non-zero and
errno shall be set to indicate the condition. If an error occurs, iconv() shall return (size_t)-1 and set
errno to indicate the error.
ERRORS
The iconv() function shall fail if:
EILSEQ Input conversion stopped due to an input byte that does not belong to the input codeset.
E2BIG Input conversion stopped due to lack of space in the output buffer.
EINVAL Input conversion stopped due to an incomplete character or shift sequence at the end of the input
buffer.
The iconv() function may fail if:
EBADF The cd argument is not a valid open conversion descriptor.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
The inbuf argument indirectly points to the memory area which contains the conversion input data. The
outbuf argument indirectly points to the memory area which is to contain the result of the conversion.
The objects indirectly pointed to by inbuf and outbuf are not restricted to containing data that is
directly representable in the ISO C standard language char data type. The type of inbuf and outbuf, char
**, does not imply that the objects pointed to are interpreted as null-terminated C strings or arrays of
characters. Any interpretation of a byte sequence that represents a character in a given character set
encoding scheme is done internally within the codeset converters. For example, the area pointed to
indirectly by inbuf and/or outbuf can contain all zero octets that are not interpreted as string
terminators but as coded character data according to the respective codeset encoding scheme. The type of
the data (char, short, long, and so on) read or stored in the objects is not specified, but may be
inferred for both the input and output data by the converters determined by the fromcode and tocode
arguments of iconv_open().
Regardless of the data type inferred by the converter, the size of the remaining space in both input and
output objects (the intbytesleft and outbytesleft arguments) is always measured in bytes.
For implementations that support the conversion of state-dependent encodings, the conversion descriptor
must be able to accurately reflect the shift-state in effect at the end of the last successful
conversion. It is not required that the conversion descriptor itself be updated, which would require it
to be a pointer type. Thus, implementations are free to implement the descriptor as a handle (other than
a pointer type) by which the conversion information can be accessed and updated.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
iconv_open(), iconv_close(), mbsrtowcs()
The Base Definitions volume of POSIX.1‐2017, <iconv.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original
IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 ICONV(3POSIX)