FGETC(P) POSIX Programmer's Manual FGETC(P)
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 associ-
ated 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
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 read-
EINTR The read operation was terminated due to the receipt of a signal, and no data was
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 ignor-
ing 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 stream.
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 capabil-
ities 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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 FGETC(P)