[css] CSS fill remaining width

I know its quite late to answer this, but I guess it will help anyone ahead.

Well using CSS3 FlexBox. It can be acheived. Make you header as display:flex and divide its entire width into 3 parts. In the first part I have placed the logo, the searchbar in second part and buttons container in last part. apply justify-content: between to the header container and flex-grow:1 to the searchbar. That's it. The sample code is below.

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#header {_x000D_
  background-color: #323C3E;_x000D_
  justify-content: space-between;_x000D_
  display: flex;_x000D_
}_x000D_
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#searchBar, img{_x000D_
  align-self: center;_x000D_
}_x000D_
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#searchBar{_x000D_
  flex-grow:1;_x000D_
  background-color: orange;_x000D_
  padding: 10px;_x000D_
}_x000D_
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#searchBar input {_x000D_
  width: 100%;_x000D_
}_x000D_
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.button {_x000D_
  padding: 22px;_x000D_
}_x000D_
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.buttonsHolder{_x000D_
  display:flex;_x000D_
}
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<div id="header" class="d-flex justify-content-between">_x000D_
    <img src="img/logo.png" />_x000D_
    <div id="searchBar">_x000D_
      <input type="text" />_x000D_
    </div>_x000D_
    <div class="buttonsHolder">_x000D_
      <div class="button orange inline" id="myAccount">_x000D_
        My Account_x000D_
      </div>_x000D_
      <div class="button red inline" id="basket">_x000D_
        Basket (2)_x000D_
      </div>_x000D_
    </div>_x000D_
</div>
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