====== Use Grep And Regular Expressions To Analyze Text ======

**General Information**

Pattern matching with grep. 

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Filter lines that start with (^) a comment (#) in myfile.txt
<code bash>
grep "^#" myfile.txt
</code>

\\
Filter for "auth", ignore case
<code bash>
grep -i "auth" /etc/ssh/ssh_config
</code>

\\
Common Grep Options
  * -i => ignore case
  * -v => invert match (show non-matching lines)
  * -c => output the count of matches (or count of non-matching if used with -v)
  * -o => print only the matched parts of the matching line
  * -n => prefix each line of output with the line number

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Regular Expression Matching
  * ^ => starts with
  * $ => ends with
  * [ab] => match a or b
  * [^ab] => do not match a or b
  * ? => previous item optional (match 0 or 1 time)
  * * => previous item matched zero or more times
  * + => previous item matched one or more times
  * . => match any single character (the period)
  * {x} => previous item matched exactly x times
  * {x,} => previous item matched x or more times
  * {,y} => previous item matched at max y times
  * {x,y} => previous item matched at least x times, but not more than y times

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