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



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

NAME
       fgetc -- get a byte from a stream

SYNOPSIS
       #include <stdio.h>

       int fgetc(FILE *stream);

DESCRIPTION
       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.1-2017
       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 fgetc().

       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().

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 thread 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 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.

       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
       Section 2.5, Standard I/O Streams, feof(), ferror(), fgets(), fread(),
       fscanf(), getchar(), getc(), gets(), ungetc()

       The Base Definitions volume of POSIX.1-2017, <stdio.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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.opengroup.org/unix/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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                             FGETC(3)
