NAME

       ungetc - push byte back into input stream

SYNOPSIS

       #include <stdio.h>

       int ungetc(int c, FILE *stream);

DESCRIPTION

       The  ungetc()  function shall push the byte specified by c (converted to an unsigned char)
       back onto the input stream pointed to by stream. The pushed-back bytes shall  be  returned
       by  subsequent  reads  on  that stream in the reverse order of their pushing. A successful
       intervening call (with the stream pointed to by stream) to a file-positioning  function  (
       fseek(),  fsetpos(),  or rewind()) shall discard any pushed-back bytes for the stream. The
       external storage corresponding to the stream shall be unchanged.

       One byte of push-back shall be provided. If ungetc() is called too many times on the  same
       stream  without  an  intervening  read  or  file-positioning operation on that stream, the
       operation may fail.

       If the value of c equals that of the macro EOF, the operation shall  fail  and  the  input
       stream shall be left unchanged.

       A  successful  call  to ungetc() shall clear the end-of-file indicator for the stream. The
       value of the file-position indicator for  the  stream  after  reading  or  discarding  all
       pushed-back bytes shall be the same as it was before the bytes were pushed back. The file-
       position indicator is decremented by each successful call to ungetc(); if its value was  0
       before a call, its value is unspecified after the call.

RETURN VALUE

       Upon  successful  completion, ungetc() shall return the byte pushed back after conversion.
       Otherwise, it shall return EOF.

ERRORS

       No errors are defined.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       fseek() , getc() , fsetpos() , read() , rewind() , setbuf() , 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, 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
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .