UNGETC(3) NEWLIB UNGETC(3)NAME
4.66 `ungetc'--push data back into a stream
SYNOPSIS
#include <stdio.h>
int ungetc(int C, FILE *STREAM);
int _ungetc_r(struct _reent *REENT, int C, FILE *STREAM);
DESCRIPTION
`ungetc' is used to return bytes back to STREAM to be read again. If C
is EOF, the stream is unchanged. Otherwise, the unsigned char C is put
back on the stream, and subsequent reads will see the bytes pushed back
in reverse order. Pushed byes are lost if the stream is repositioned,
such as by `fseek', `fsetpos', or `rewind'.
The underlying file is not changed, but it is possible to push back
something different than what was originally read. Ungetting a charac‐
ter will clear the end-of-stream marker, and decrement the file posi‐
tion indicator. Pushing back beyond the beginning of a file gives
unspecified behavior.
The alternate function `_ungetc_r' is a reentrant version. The
extra argument REENT is a pointer to a reentrancy structure.
RETURNS
The character pushed back, or `EOF' on error.
PORTABILITY
ANSI C requires `ungetc', but only requires a pushback buffer of one
byte; although this implementation can handle multiple bytes, not all
can. Pushing back a signed char is a common application bug.
Supporting OS subroutines required: `sbrk'.
SEE ALSOungetc is part of the library. The full documentation for is main‐
tained as a Texinfo manual. If info and are properly installed at your
site, the command
info
will give you access to the complete manual.
NEWLIB April 2010 UNGETC(3)
