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() 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:
The O_NONBLOCK flag is set for the file descriptor underlying stream
and the process would be delayed in the fgetc()
The file descriptor underlying stream is not a valid file descriptor
open for reading.
The read operation was terminated due to the receipt of a signal,
and no data was transferred.
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:
Insufficient storage space is available.
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
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