FGETC(3P) POSIX Programmer's Manual FGETC(3P)
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.
fgetc - get a byte from a stream
int fgetc(FILE *stream);
If the end-of-file indicator for the input stream pointed to by stream is
not set and a next byte is present, the fgetc() function shall obtain the
next byte as an unsigned char converted to an int, from the input stream
pointed to by stream, and advance the associated file position indicator
for the stream (if defined). Since fgetc() operates on bytes, reading a
character consisting of multiple bytes (or "a multi-byte character") may
require multiple calls to fgetc().
The fgetc() function may mark the st_atime field of the file associated
with stream for update. The st_atime field shall be marked for update by
the first successful execution of fgetc(), fgets(), fgetwc(), fgetws(),
fread(), fscanf(), getc(), getchar(), gets(), or scanf() using stream
that returns data not supplied by a prior call to ungetc() or ungetwc().
Upon successful completion, fgetc() shall return the next byte from the
input stream pointed to by stream. 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 fgetc() shall return EOF. If a
read error occurs, the error indicator for the stream shall be set,
fgetc() shall return EOF, and shall set errno to indicate the error.
The fgetc() 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 process would be delayed in the fgetc() operation.
EBADF The file descriptor underlying stream is not a valid file
descriptor open for reading.
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 process is ignoring or blocking the
SIGTTIN signal or the process group is orphaned. This error may
also be generated for implementation-defined reasons.
The file is a regular file and an attempt was made to read at or
beyond the offset maximum associated with the corresponding
The fgetc() 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.
If the integer value returned by fgetc() is stored into a variable of
type char and then compared against the integer constant EOF, the
comparison may never succeed, because sign-extension of a variable of
type char on widening to integer is implementation-defined.
The ferror() or feof() functions must be used to distinguish between an
error condition and an end-of-file condition.
feof(), ferror(), fopen(), getchar(), getc(), the Base Definitions volume
of IEEE Std 1003.1-2001, <stdio.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 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
IEEE/The Open Group 2003 FGETC(3P)