Grep
The grep command-line utility is used for searching plain-text data sets for lines that match a regular expression. It is generally used in collaboration with other Linux commands, such as ls, cat, etc., to provide powerful search functionality in files, consoles, IO streams, etc.
Options
| Options | Values | Description |
|---|---|---|
| -i | NA | Case-insensitive search |
| -A <LINE_NO> | NA | Display LINE_NO lines after the match |
| -B <LINE_NO> | NA | Display LINE_NO lines before the match |
| -C <LINE_NO> | NA | Display LINE_NO lines both before and after the match(around) |
| -r | NA | Recursive search across all nested files and folders |
| -v | NA | Invert the search results |
| -c | NA | Count the number of search results |
| -l | NA | Display only the file names which have the searched results |
| -o | NA | Show only searched results, NOT the whole line |
| -e “REGEX_PATTERN” | NA | Specify the regex pattern to be searched |
| -n | NA | Line number for the search results |
Packages and Install
| OS | Package Install CMD |
|---|---|
| Debian/ubuntu | apt install grep |
| Centos/fedora(dnf, microdnf, rpm, yum) | yum install grep |
| Arch (pacman) | pacman -S grep |
| Alpine (apk-docker) | apk –no-cache add grep |
Examples
For Detailed Regex related docs, please refer regex
- Search a match string in a file
grep "test" test_file.txt- Recursively search all the files and in the sub-directory
grep -r "test" /some/tmp/dir/*- Get the lines that do not start with a vowel, along with line numbers
grep -v -n -e "^[aeiouAEIOU].*" test_file.txt- Case-insensitive search with 2 lines above and below to display in all the files in the current working directory.
grep -i -A 2 -B 2 "test" *- Get all the details for the wired ethernet network interface
ifconfig | grep -A 4 ens*- Get all the Java processes running.
ps aux | grep java