<table cellpadding="5"><tr><th style="border-bottom: 1px solid black;text-align:left;">Linux Command</th><th style="border-bottom: 1px solid black;text-align:left;">Purpose</th></tr><trvalign="top"><td>'''ps'''</td><td>x</td></<tr><tr><td>top</td><td>Square brackets ([ ]) to represent and match for the <br>'''character enclosed within the square brackets'''.<br>It represents ONLY ONE character - it's like a<br>'''Question Mark (?)''' but with '''conditions or restrictions'''</td></tr><tr><td>'''[! ]'''</td><td>Square brackets containing an exclamation mark immediately after<br>the open square bracket ([! ]) to represent and match and<br>'''OPPOSITE''' character for the character enclosed within the square brackets.</td></tr></table>