Grep stands for “Global Regular Expression Print”, grep is a search operation. It is one of the widely used command in unix. We are using grep mostly finding words. We can analyze the large sets of log files with help of grep command.
Syntax of grep command is
The options are
- grep-v: It is a negative search. You can display the lines that are not matched with our search operation.
- grep-n: Display line numbers
- grep-h: Display file name.
- grep-c: Count the number of matches.
- grep-o-b: Display position of matches string
- grep-L: Display file name that do not contain the pattern
- grep-l: Case insensitive search
Examples of Grep Command
1. Search for string in a file
grep "name" file.txt
This is the basic unix command. This searches for the string "name" in the file name file.txt. It displays all the lines contain with the word "name".
2.Search for a string in multiple files
grep "name" file1 file2
grep -B 2 "name" file.txt
This will prints matched lines along with the two lines before matched lines
4.Displaying lines after match
grep -A 2 "name" file.txt
This will prints matched lines along with the two lines after the matched lines
5.Count the number of matches
grep -c "name" file.txt
Using this command find the number of lines that matches to the given string.
6.Display the line numbers
grep -n "name" file.txt
7.Matching the lines start with a string
grep "^start" file.txt
The symbol "^" shows that starting position of line
8.Matching the lines end with a string
grep "end$" file.txt
The symbol "$" shows that ending position of line
