1 /* ungetc.c 4.3 85/02/13 */ 2 3 #include <stdio.h> 4 5 ungetc(c, iop) 6 register FILE *iop; 7 { 8 if (c == EOF || (iop->_flag & (_IOREAD|_IORW)) == 0 || 9 iop->_ptr == NULL || iop->_base == NULL) 10 return (EOF); 11 12 if (iop->_ptr == iop->_base) 13 iop->_ptr++; 14 15 iop->_cnt++; 16 *--iop->_ptr = c; 17 18 return (c); 19 } 20