NAME

fputwc — put a wide-character code on a stream

SYNOPSIS

#include <stdio.h>
#include <wchar.h>

wint_t fputwc(wchar_t wc, FILE *stream);


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2024 defers to the ISO C standard.

The fputwc() function shall write the character corresponding to the wide-character code wc to the output stream pointed to by stream, at the position indicated by the associated file-position indicator for the stream (if defined), and advances the indicator appropriately. If the file cannot support positioning requests, or if the stream was opened with append mode, the character is appended to the output stream. If an error occurs while writing the character, the shift state of the output file is left in an undefined state.

^[CX] The last data modification and last file status change timestamps of the file shall be marked for update between the successful execution of fputwc() and the next successful completion of a call to fflush() or fclose() on the same stream or a call to exit() or abort().

The fputwc() function shall not change the setting of errno if successful.

RETURN VALUE

Upon successful completion, fputwc() shall return wc. Otherwise, it shall return WEOF, ^[CX]  errno shall be set to indicate the error, and for errors other than [EILSEQ] the error indicator for the stream shall be set; ^[CX]  the error indicator for the stream shall also be set for [EILSEQ] errors.

ERRORS

The fputwc() function shall fail if either the stream is unbuffered or data in the stream's buffer needs to be written, and:

[EAGAIN]

^[CX] The O_NONBLOCK flag is set for the file descriptor underlying stream and the thread would be delayed in the write operation.

[EBADF]

^[CX] The file descriptor underlying stream is not a valid file descriptor open for writing.

[EFBIG]

^[CX] An attempt was made to write to a file that exceeds the maximum file size.

[EFBIG]

^[CX] An attempt was made to write to a file that exceeds the file size limit of the process.
^[XSI] A SIGXFSZ signal shall also be generated for the thread.

[EFBIG]

^[CX] The file is a regular file and an attempt was made to write at or beyond the offset maximum associated with the corresponding stream.

[EILSEQ]

The wide-character code wc does not correspond to a valid character.

[EINTR]

^[CX] The write operation was terminated due to the receipt of a signal, and no data was transferred.

[EIO]

^[CX] A physical I/O error has occurred, or the process is a member of a background process group attempting to write to its controlling terminal, TOSTOP is set, the calling thread is not blocking SIGTTOU, the process is not ignoring SIGTTOU, and the process group of the process is orphaned. This error may also be returned under implementation-defined conditions.

[ENOSPC]

^[CX] There was no free space remaining on the device containing the file.

[EPIPE]

^[CX] An attempt is made to write to a pipe or FIFO that is not open for reading by any process. A SIGPIPE signal shall also be sent to the thread.

The fputwc() function may fail if:

[ENOMEM]

^[CX] Insufficient storage space is available.

[ENXIO]

^[CX] A request was made of a nonexistent device, or the request was outside the capabilities of the device.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

The requirement to set the error indicator for the stream on [EILSEQ] errors is CX shaded because the ISO C standard does not require it to be set for fputwc() encoding errors, although it does for fgetwc(). The next revision of the ISO C standard is expected to address this inconsistency by requiring the error indicator for the stream to be set for fputwc() encoding errors.

FUTURE DIRECTIONS

None.

SEE ALSO

2.5 Standard I/O Streams, ferror, fopen, getrlimit, setbuf

XBD <stdio.h>, <wchar.h>

CHANGE HISTORY

First released in Issue 4. Derived from the MSE working draft.

Issue 5

Aligned with ISO/IEC 9899:1990/Amendment 1:1995 (E). Specifically, the type of argument wc is changed from wint_t to wchar_t.

The Optional Header (OH) marking is removed from <stdio.h>.

Large File Summit extensions are added.

Issue 6

Extensions beyond the ISO C standard are marked.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

• The [EFBIG] and [EIO] mandatory error conditions are added.

• The [ENOMEM] and [ENXIO] optional error conditions are added.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/38 is applied, updating the [EAGAIN] error in the ERRORS section from "the process would be delayed" to "the thread would be delayed".

Issue 7

Changes are made related to support for finegrained timestamps.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0173 [105], XSH/TC1-2008/0174 [79], and XSH/TC1-2008/0175 [14] are applied.

Issue 8

Austin Group Defect 308 is applied, clarifying the handling of [EFBIG] errors.

Austin Group Defect 1669 is applied, removing XSI shading from part of the [EFBIG] error relating to the file size limit for the process.

Austin Group Defect 1769 is applied, changing the CX shading in the RETURN VALUE section.