FGETC(3P)                                           POSIX Programmer's Manual                                          FGETC(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       fgetc - get a byte from a stream

SYNOPSIS
       #include <stdio.h>

       int fgetc(FILE *stream);


DESCRIPTION
       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().

RETURN VALUE
       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.

ERRORS
       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.

       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 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.

EXAMPLES
       None.

APPLICATION USAGE
       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.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feof(), ferror(), fopen(), getchar(), getc(), the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>

COPYRIGHT
       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, Copy-
       right (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   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     FGETC(3P)