How is `grep -E` different from `grep`?

That's a great question about grep!

The main difference between grep -E and plain grep lies in the type of regular expressions they use:

• grep (basic regular expressions - BREs): By default, grep uses Basic Regular Expressions. This means that certain special characters (like ?, +, {, |, ( and )) are treated as literal characters unless they are escaped with a backslash (\). For example, (foo|bar) would literally search for "(foo|bar)" with basic grep, not "foo" or "bar".

• grep -E (extended regular expressions - EREs): The -E option tells grep to use Extended Regular Expressions. In EREs, the special characters mentioned above (?, +, {, |, ( and )) are interpreted as metacharacters (e.g., | means "OR," () for grouping, + for one or more occurrences) without needing to be escaped. This makes writing more complex patterns often simpler and more intuitive.

In essence:

• grep: You often need to escape special characters like \| to make them act as regular expression operators.
• grep -E: Special characters like | work as regular expression operators by default.

For simple string searches, like searching for "labex", there's usually no practical difference, as "labex" doesn't contain any regular expression metacharacters. However, if you were searching for, say, "apple OR banana" using regular expressions, grep -E "apple|banana" would work directly, while grep "apple\|banana" would be needed with plain grep.

Does that clarity up the distinction for you? Let me know if you have more questions!