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--- grep:regex_usage [2020/08/22 11:32] – created 192.168.1.1
+++ grep:regex_usage [2020/08/22 11:51] (current) – 192.168.1.1
@@ Line 7: / Line 7: @@
 ----
+Assuming a file exists with the following contents:
+<file>
+boot
+book
+booze
+machine
+boots
+bungie
+bark
+aardvark
+broken$tuff
+robots
+</file>
+----
+===== Basic Regex Search =====
+Search the file for lines ending with the letter e.
+<code bash>
+grep "e$" filename
+</code>
+returns:
+<code bash>
+booze
+machine
+bungie
+</code>
+----
+===== Extended Regex Search =====
+<code bash>
+grep -E "boots?" filename
+</code>
+returns:
+<code bash>
+boot
+boots
+</code>
+<WRAP info>
+**NOTE:**  **grep -E** is also known as egrep.
+The regexp command ? will match 1 or 0 occurrences of the previous character.
+</WRAP>
+----
+===== Combine Multiple Searches =====
+<code bash>
+grep -E "boot|boots" filename
+</code>
+returns:
+<code bash>
+boot
+boots
+</code>
+<WRAP info>
+**NOTE:**  The pipe **|** means 'or'.
+</WRAP>
+----
+===== Special Characters =====
+<code bash>
+grep '\$' filename
+</code>
+returns:
+<code bash>
+broken$tuff
+</code>
+<WRAP info>
+**NOTE:**
+The **-F-- option can also be used, which stands for 'fixed string' or 'fast' in that it only searches for literal strings and not regexps.
+</WRAP>