I want to replace the first instance of `<tr>` with `<tr class="active">` using the shell (bash).

However, this sed has no affect:

```
sed '0,/<tr>/s/<tr>/<tr class="active">/' FILE1 >> temp2.txt

```

temp2.txt remains

```
<tr>
  <th>set</th>
  <th>Run</th>
  <th>Continuum<br>filter</th>
  <th>Narrow Band<br>filter</th>
</tr>
<tr>
  <td><a href="#set1">1</a></td>
  <td>Run09</td>
  <td>R_Harris</td>
  <td>6605/32</td>
</tr>

```

Whereas this code changes both the first and second instance of `<tr>`

```
sed '1,/<tr>/s/<tr>/<tr class="active">/' FILE1 >> temp2.txt

```

Can anyone explain what's going on?

```
<tr class="active">
    <th>set</th>
    <th>Run</th>
    <th>Continuum<br>filter</th>
    <th>Narrow Band<br>filter</th>
</tr>
<tr class="active">
    <td><a href="#set1">1</a></td>
    <td>Run09</td>
    <td>R_Harris</td>
    <td>6605/32</td>
</tr>

```