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.
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.1‐2008 defers to the ISO C standard.
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
The fgetc() 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 fgetc(), fgets(), fread(), fscanf(), getc(), getchar(),
getdelim(), getline(), gets(), or scanf() using stream that returns
data not supplied by a prior call to ungetc().
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 thread would be delayed in the fgetc()
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 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.
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.
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/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
IEEE/The Open Group 2013 FGETC(3P)