Minix1.5/lib/ansi/ungetc.c

#include <lib.h>
#include <stdio.h>

int ungetc(ch, iop)
int ch;
FILE *iop;
{
  if (ch < 0 || !testflag(iop, READMODE) || testflag(iop, UNBUFF))
	return(EOF);

  if (iop->_count >= BUFSIZ) return(EOF);

  if (iop->_ptr == iop->_buf) iop->_ptr++;

  iop->_count++;
  *--iop->_ptr = ch;
  return(ch);
}