UNGETC(3) BSD Library Functions Manual UNGETC(3)
NAME
ungetc — un-get character from input stream
LIBRARY
Standard C Library (libc, −lc)
SYNOPSIS
#include <stdio.h>
int
ungetc(int c, FILE *stream);
DESCRIPTION
The ungetc() function pushes the character c (converted to an unsigned char) back onto the input stream pointed to by stream. The pushed-back characters will be returned by subsequent reads on the stream (in reverse order). A successful intervening call, using the same stream, to one of the file positioning functions (fseek(3), fsetpos(3), or rewind(3)) will discard the pushed back characters.
One character of push-back is guaranteed, but as long as there is sufficient memory, an effectively infinite amount of pushback is allowed.
If a character is successfully pushed-back, the end-of-file indicator for the stream is cleared. 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 VALUES
The ungetc() function returns the character pushed-back after the conversion, or EOF if the operation fails. If the value of the argument c character equals EOF, the operation will fail and the stream will remain unchanged.
SEE ALSO
fseek(3), getc(3), setvbuf(3), ungetwc(3)
STANDARDS
The ungetc() function conforms to ISO/IEC 9899:1990 (‘‘ISO C90’’).
BSD June 4, 1993 BSD