Linux grep command usage and regular expressions

1. What is grep

   grep (Global search REgular expression and Printout the line), which is a globally searchable regular expression and prints out matching rows, is a powerful text-search tool in the Linux system that is based on user-specified "patterns ( pattern) "Filters the target text to show rows that are matched by the pattern.

2. Basic syntax format for grep commands

   grep [Options] PATTERN [FILE ...]

3. Common options for grep

   -V: Reverse the matching content

   -O: Show only what matches to

   -I: Ignore case

   -N: Show line numbers

   --color=auto: Using colors to display matching content

   The basic usage of grep in conjunction with regular expressions

   .: Any single character

   []: Any single character of the characters contained in parentheses, such as

   Pure numbers: [[:d Igit:]] or [0-9]

   lowercase letters: [[: Lower:]] or [A-z]

   Capital letters: [[: Upper:]] or [A-z]

   Uppercase and lowercase letters: [[: Alpha:]] or [a-za-z]

   Numbers plus letters: [[: Alnum:]] or [0-9a-za-z]

   whitespace characters: [[: Space:]]

   Punctuation: [[:p UNCT:]]

   
   

Linux grep command usage and regular expressions