How to perform grep operation on all files in a directory?

The grep command in Linux is used to filter searches in a file for a particular pattern of characters. It is one of the most used Linux utility commands to display the lines that contain the pattern that we are trying to search.

Normally, the pattern that we are trying to search in the file is referred to as the regular expression.

Syntax

grep [options] pattern [files]

While there are plenty of different options available to us, some of the most used are −

-c : It lists only a count of the lines that match a pattern
-h : displays the matched lines only.
-i : Ignores, case for matching
-l : prints filenames only
-n : Display the matched lines and their line numbers.
-v : It prints out all the lines that do not match the pattern

Now, let’s consider a case where we want to find a particular pattern in all the files in a particular directory, say dir1.

Syntax

grep -rni "word" *

In the above command replace the “word” placeholder with

For that we make use of the command shown below −

grep -rni "func main()" *

The above command will try to find a string “func main()” in all the files in a particular directory and also in the subdirectories as well.

Output

main.go:120:func main() {}

In case we only want to find a particular pattern in a single directory and not the subdirectories then we need to use the command shown below −

grep -s "func main()" *

In the above command we made use of the -s flag which will help us to not get a warning for each subdirectory that is present inside the directory where we are running the command.

Output

main.go:120:func main() {}

Another command that we can make use of is the find command.

Command

find . -name "*.go" -exec grep -H "func main" {} \;

Output

./main.go:func main() {