#USE GREP COMMAND IN LINUX HOW TO#

The -c option counts the number of lines that match the pattern instead of displaying the actual lines. The -r option enables recursive searching in the specified directory and its subdirectories.Ĭounting matches: grep -c 'pattern' file.txt Recursive search in directories: grep -r 'pattern' directory/ The -v option inverts the match, displaying all lines that do not contain the specified pattern. The -i option makes the search case-insensitive, so it matches both uppercase and lowercase versions of the pattern. This command searches for the specified “pattern” in the “file.txt” and displays all matching lines.Ĭase-insensitive search: grep -i 'pattern' file.txt

#USE GREP COMMAND IN LINUX HOW TO#

Here are some common use cases and examples of how to use the grep command:īasic pattern matching: grep 'pattern' file.txt It is commonly used in Unix-like operating systems, including Linux and macOS. To output a list of file names that do not contain a matching word or pattern, use the -L or -files-without-match flags.The grep command is a powerful tool used for searching and filtering text based on patterns. grep -l -r 'student1' /var/logs Show file names without matches To output only file names that contain a matching word or pattern, use the -l or -files-with-matches flags in your command. Grep can output file names only, if you are more interested in finding files with a matching word or pattern inside of them. grep -I -r 'student1' /opt/myapp Show only file names of matches If you find yourself wanting to match files from a directory or nested directory, you may want to exclude binary files in your search. grep -v 'error' /var/log/apache2 Ignore Binary Files To perform inverse matches with grep use the -v flag.įor example, if you wanted to return all log entries except errors, you would use the following command. grep -c 'error' /var/logs/apache2 Inverse Matches with GrepĪn inverse match returns results that do not match a word or pattern used with grep. Grep supports counting matches with the -c flag.

You may be more interested in knowing the number of matches rather than outputting the matches to file or screen. grep 'warning|error' /var/log/apache2 Counting Matches with Grep

Each word separated by that character will be matched separately.įor example, to find the words “warning” or “error” in the output of all of your Apache web server logs, you would run the following command. To search multiple words, use the | character as a delimination. Multiple words can be matched against using grep, which is very useful when you’re not sure what you are looking for or want to find multiple items. grep -r 'error' /var/logs Grep Searching Multiple Words To perform a recursive search, where grep finds a string in files of all nested, child directories, you can use the -r or -R flags. The grep command will not recursively search directories by default. grep -i Student1 ~/class/students Recursive Directory Searches If do not know the case or want to find all cases, you add the -i flag. It search for using the exact case specified at the command-line. Grep will search each file and output the matching line from each. The grep command allows us to chain multiple files into our search by adding them at the end of the command.įor example, to find the world hello in the files file1, file2, file3 and file4, we would run the command as follows. You may find yourself wanting to search multiple files for a matching string. grep 'hello' file.txt Multiple File Grep Search For example, to find the word hello in a file named file.txt we would run the following command. To find a word inside of a single file we specify the word we want matched and file to search. It is used to search a single file or an entire directory, including child directories, for a matching string. The grep command in Linux is a utility used to search any given input files for one or more matching words or patterns. In this tutorial, you will learn how to use the grep command in Linux, Unix and OSX, with examples of common use cases.

Use grep command in linux