HTML

bootstrap 4 search bar

<form class="form-inline">
  <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
  <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
</form>

search bar bootstrap

<div class="input-group">
	<input id="search-input" type="search" class="form-control" placeholder="Search anything...">  
  	<button id="search-button" type="button" class="btn btn-primary">
    <i class="fa fa-search"></i>
  	</button>
</div>

box search bootstrap

<div class="input-group">
  <div class="form-outline">
    <input id="search-input" type="search" id="form1" class="form-control" />
    <label class="form-label" for="form1">Search</label>
  </div>
  <button id="search-button" type="button" class="btn btn-primary">
    <i class="fas fa-search"></i>
  </button>
</div>

Bootstrap 4 Search Box

<div class="input-group mb-3">
  <input type="text" class="form-control" placeholder="Search" aria-label="Search" aria-describedby="basic-addon2">
  <div class="input-group-append">
    <span class="input-group-text" id="basic-addon2">Search/span>
  </div>
</div>