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edited the grep section #359

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4 changes: 3 additions & 1 deletion shell_tools_101.rst
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Expand Up @@ -448,7 +448,9 @@ Characters Meaning
Note that there's almost always more than one way to express a particular pattern.
When you're developing a regular expression, it can be helpful to test it on simplified input to see what it catches.
To test a regex for various spellings of opsschool, you might put a variety of spellings in a file and then grep it to see which regex catches which spellings.

Lastly, there is a big difference between a plain ``grep`` call and a ``grep -E`` call (Basic RE vs. Extended RE). In BRE, any of these characters need a preceding backslash in order for them to take effect: {}, +, ?, |
If not preceded by a backslash they are treated as normal characters.
E.g. ``grep "ops \?school"`` is equivalent to ``grep -E "ops ?school"``
.. code-block:: console

user@opsschool ~$ cat ops.txt
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