fgetwc3p

Usage

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

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.

Overview

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.1‐2017 defers to the ISO C standard.

The fgetwc() function shall obtain the next character (if present) from the input stream pointed to by stream, convert that to the corresponding wide-character code, and advance the associated file position indicator for the stream (if defined).

If an error occurs, the resulting value of the file position indicator for the stream is unspecified.

The fgetwc() function may mark the last data access timestamp of the file associated with stream for update. The last data access timestamp shall be marked for update by the first successful execution of fgetwc(), fgetws(), fwscanf(), getwc(), getwchar(), vfwscanf(), vwscanf(), or wscanf() using stream that returns data not supplied by a prior call to ungetwc().

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

Return value

Upon successful completion, the fgetwc() function shall return the wide-character code of the character read from the input stream pointed to by stream converted to a type wint_t. If the end-of-file indicator for the stream is set, or if the stream is at end-of-file, the end-of-file indicator for the stream shall be set and fgetwc() shall return WEOF. If a read error occurs, the error indicator for the stream shall be set, fgetwc() shall return WEOF, and shall set errno to indicate the error. If an encoding error occurs, the error indicator for the stream shall be set, fgetwc() shall return WEOF, and shall set errno to indicate the error.

Errors

The fgetwc() function shall fail if data needs to be read and:

EAGAIN

The O_NONBLOCK flag is set for the file descriptor underlying stream and the thread would be delayed in the fgetwc() operation.

EBADF

The file descriptor underlying stream is not a valid file descriptor open for reading.

EILSEQ

The data obtained from the input stream does not form a valid character.

EINTR

The read operation was terminated due to the receipt of a signal, and no data was transferred.

EIO

A physical I/O error has occurred, or the process is in a background process group attempting to read from its controlling terminal, and either the calling thread is blocking SIGTTIN or the process is ignoring SIGTTIN or the process group of the process is orphaned. This error may also be generated for implementation-defined reasons.

EOVERFLOW

The file is a regular file and an attempt was made to read at or beyond the offset maximum associated with the corresponding stream.

The fgetwc() function may fail if:

ENOMEM

Insufficient storage space is available.

ENXIO

A request was made of a nonexistent device, or the request was outside the capabilities of the device.

The following sections are informative.

Examples

None.

Application usage

The ferror() or feof() functions must be used to distinguish between an error condition and an end-of-file condition.

Rationale

None.

Future directions

None.