"Linux series", "Basic Edition", chapter fourth, the regular expression of Shell Foundation

Regular expressions for 4. shell Basics     4.1  Regular strings are a string of rules          4.1 grep             4.1.1  Format: grep [-cinrvabc]  ' word '  filename             4.1.2 -c //count, indicating number of rows              4.1.3 -i //Case insensitive              4.1.4 -n  //Display line number              4.1.5 -r  //traversing all subdirectories              4.1.6 -v  //take anti-            4.1.7  -a  //followed by numbers, filtering out rows that meet the requirements and the following n rows              4.1.8 -b  //the same, filtering out the rows that meet the requirements and the N rows above             4.1.9 -c   //Ibid, simultaneously filtering out the line that meets the requirements and the N rows              4.1.10  extension                  4.1.10.1  single quote,  single quotes are treated as a single string                  4.1.10.2  double quote, double quotes are treated as a single string, preventing wildcard expansion, but allowing variable expansion                 4.1.10.3   backticks, the inverted quotation marks are treated as strings and can include command columns

"Linux series", "Basic Edition", chapter fourth, the regular expression of Shell Foundation