.block {
width: 100vw;
height: 20vh;
position: fixed;
top: 0;
left: 0;
}<form action="">
<input name="f" id="f" type="file" onchange="ept();"></input>
<input name="t" id="t" type="text"></input>
</form>function ept() {
document.getElementById('t').value = document.getElementById('f').value;
}