![]() For example, to find all lines that end with none in sshd_config, use grep like this: $ grep none$ /etc/ssh/sshd_config You can also look for lines that end with a text pattern by using the $ operator. For example, to search for a pattern that contains the word Port followed by numbers, use this regular expression: $ grep -E "Port " /etc/ssh/sshd_config You can also use extended regular expressions with the command-line parameter -E. This time grep returned only the line that started with Port since, in the second line, the expression Port is in the middle. For example, to find only lines that start with the word Port, you can use the regular expression operator ^, like this: $ grep ^Port /etc/ssh/sshd_config To avoid that, you can use regular expressions to be more specific about what you're looking for. In other cases, grep could find too many entries that you're not interested in, requiring you to sort through them to find the desired information. In some cases, that's exactly what you want. The line you were looking for, Port 22, and an additional line containing the search pattern. In the previous example, when you searched for Port in the SSH configuration file, grep returned two lines. Notice that grep finds all lines that match the text pattern regardless of where the pattern is located. For example, to find which port the Secure Shell (SSH) daemon uses, search for Port in file /etc/ssh/sshd_config: $ grep Port /etc/ssh/sshd_config To do this, type grep followed by the text pattern to search for and the file name to search in. The most basic way to use grep is searching for text in a single file. ![]() This article covers how to use the grep command to find text. Using grep, you can quickly find text matching a regular expression in a single file, a group of files, or text coming from stdin using the shell pipe operator. However, its main functionality is still the same. Grep evolved over the years, and the most common version available today for Linux, GNU grep, has additional features such as colored output. This utility was originally developed for the Unix operating system in the early 1970s. The most common way to find text in a Linux system is using the command-line utility grep. Learning path: Deploy a cluster in Red Hat OpenShift Service on AWS (ROSA).Get a Red Hat Learning Subscription trial.Learn about Red Hat Certified System Administrator (RHCSA) certification.Explore Red Hat training and certification options.$ grep -E "ismail|ali" *.txt Match In Multiple FilesĪs we can see matched files also printed with the matched text. We have also the ability to search and match in multiple files. We will use \. )" data.txt Match IP Address or Domain Name Match In Multiple Files This may be a regular operation while searching in log files. Now we will look useful example which provides IP address or domain names. $ grep -E "is.ail|al." data.txt Match Multiple Pattern or Regex Match IP Address or Domain Name We can specify standard regular expression with the same way. Now we want to use multiple regular expression or pattern in our match term. $ grep -E "ismail|ali" data.txt Match Multiple Strings Match Multiple Pattern or Regex The matching strings will be ismail and ali . In this example we will use a file named data.txt as a text. We will match given multiple strings inside a given text. E means extended grep which will enable extended regular expression features to use. We can use grep command with -E option or egrep command which is the alias of the grep -E . How To Use Regular Expression – Regex In Bash Linux? Grep -E or Egrepīefore starting examples we look different commands which provides same functionality. If you need more general tutorial about regex please look following article. In this tutorial we will look different examples about these features. One of the most used feature is to match two or more, multiple string, patterns or regex. ![]() ![]() Grep provides a lot of features to match strings, patterns or regex in a given text. ![]()
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