bionic (3) fgetc.3posix.gz

PROLOG

       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.

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.1‐2008 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 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.1‐2008, <stdio.h>

COPYRIGHT

       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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .