Grep Command In Linux
The 'grep' command stands for "global regular expression print". grep command filters the content of a file which makes our search simple.
Grep With Pipe
The 'grep' command is often used with pipe (|).
Syntax:
command | grep <searchWord>
Example:
cat marks.txt | grep 9
Look at the above snapshot, grep command filters all the data containing '9'.
Grep Without Pipe
It may be used without pipe as well.
Syntax:
grep <searchWord> <file name>
Example:
grep 9 marks.txt
Look at the above snapshot, the grep command accomplish the same thing as the previous example but without pipe.
Grep Options
grep -vM: The 'grep -v' command reveals lines not matching the provided term.
Syntax:
grep -v <searchWord> <fileName>
Example:
grep -v 9 marks.txt
grep -v 9 marks.txt
Look at the preceding snapshot, program "grep -v 9 marks.txt" reveals lines that don't include our search phrase '9'.
Grep -i
The 'grep -i' command filters output in a case-insensitive way.
Syntax:
grep -i <searchWord> <fileName>
Example:
grep -i red exm.txt
Look at the preceding snapshot, program "grep -i red exm.txt" reveals all lines containing 'red' whether in upper case or lower case.
grep -A/ grep -B/ grep -C
grep -A command is used to display the line after the result.
grep -B command is used to display the line preceding the result.
grep -C command is used to display the line after and line before the result.
You may use (A1, A2, A3.....)(B1, B2, B3....)(C1, C2, C3....) to show any number of lines.
Syntax:
grep -A<lineNumber> <searchWord> <fileName>
grep -B<lineNumber> <searchWord> <fileName>
grep -C<lineNumber> <searchWord> <fileName>
Example:
grep -A1 yellow exm.txt
grep -B1 yellow exm.txt
grep -C1 yellow exm.txt
Look at the above snapshot, command "grep -A1 yellow exm.txt" shows searched line with next following line, the command "grep -B1 yellow exm.txt" displays searched line with one previous line and command "grep -C1 yellow exm.txt" displays searched line with one preceding and succeeding line.
