怎么样使用css实现文字过长自动隐藏功能？

overflow: hidden;
text-overflow: ellipsis;
white-space: nowrap; 

p{
position:relative;
line-height:1.4em;
height:4.2em;/* 3 倍line-height 多少倍就是多少行*/
overflow:hidden;
}
.p::after {
content:"...";
font-weight:bold;
position:absolute;
bottom:0;
right:0;
padding:0 20px 1px 45px;
background: -webkit-linear-gradient(left, transparent, #fff 55%);
background: -o-linear-gradient(right, transparent, #fff 55%);
background: -moz-linear-gradient(right, transparent, #fff 55%);
background: linear-gradient(to right, transparent, #fff 55%);
}