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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 dif-
       fer (consult 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 con-
       dition.

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, Stan-
       dard  for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica-
       tions 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 Stan-
       dard, the original IEEE and The Open Group Standard is the referee  document.  The  original  Standard  can  be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                            FGETC(3P)