Grep -E "(^| )webservertalk( |$)" file.txt Let’s search for a line that matches the exact word webservertalk. In order to print the exact match, you will need to search for a word with leading or trailing white space characters. That means this command does not work if you want to find the whole word in the middle of the line. Let’s run the following command to understand it better:Īs you can see, the above command is unable to print all lines that contain the word “ webservertalk“. You can also use the grep command to find an exact match by using the beginning(^) and ending($) character. It does not perform well if you want to print an exact match of the whole word and remove non-relevant matches. You can use -w option to search a specific word:Īs you can see, the above command prints all lines containing word webservertalk. In the following example, we will search a word webservertalk from a file.txt. Create a Sample Fileįirst, let’s create a sample file to explain all the examples with hands-on practical.īasically, the grep command consists of three parts including:
Use grep and reg exp to find word in file how to#
In this tutorial, we will show you how to search for an Exact Pattern with some practical examples. You can also use the grep command to find only those lines that completely match the search string. You can use it with a regular expression to be more flexible at finding strings. When you try to work backward from the final version to see what it does, it’s a different challenge altogether.įor example, look at this command: grep -E '^(: An interval operator is applied to the first character and converts it to 16 characters, all of which are digits.Grep is a Linux command-line tool used to search for a specific string or text in the file. They tend to increase in sophistication over time. When people write complicated regexes, they usually start off small and add more and more sections until it works. Some regexes can quickly become difficult to visually parse. We put it all together in the following command: grep -E 'H*man' geeks.txt *: The asterisk here represents any number of lowercase letters.: The next character can be any lowercase letter in this range.In our next command, we’ll use the a-z range specifier. The following search pattern matches sequences that start with “J,” followed by an “o” or “s,” and then either an “e,” “h,” “l,” or “s”: grep -E 'J' geeks.txt You can also use as many character classes as you want in a search pattern. d-p: All lowercase letters from “d” to “p.” These free-format styles allow you to define your own range.a-z: All lowercase letters from “a” to “z.”.A-Z: All uppercase letters from “A” to “Z.”.These range indicators save you from having to type every member of a list in the search pattern. You can use shortcuts to specify the lists in character classes. We’ll use the boundary operator ( \B) at both ends of the search pattern to find a sequence of characters that must be inside a larger word: grep -E '\bGlenn\b' geeks.txt grep -E '\Bway\B' geeks.txt To create a search pattern that looks for an entire word, you can use the boundary operator ( \b). The second command produces the desired result. Now, we type the following, using the end of word anchor ( />) (which points to the right, or the end of the word): grep -E 'y\>' geeks.txt If you want to reduce the output to the bare minimum, you can use the -c (count) option. To do so, we type the following: grep -E -n -o 'o' geeks.txt This can be useful if you need to quickly scan a list for duplicate matches on any of the lines. It only displays the matching character sequence, not the surrounding text. We type the following: grep -E -n 'o' geeks.txtĪnother handy grep trick you can use is the -o (only matching) option. However, sometimes, you might want to know where in a file the matching entries are located. This is a grep trick-it’s not part of the regex functionality. If you want grep to list the line number of the matching entries, you can use the -n (line number) option. RELATED: How Do You Actually Use Regex? Line Numbers and Other grep Tricks We’ll see more functionality with our search patterns as we move forward. It doesn’t mean anything other than what we typed: double “o” characters. Our result set, as expected, is much smaller, and our search term is interpreted literally.
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