-c: Prints the line count that matches the pattern i.e “Linux”.

-i: Ignore the case sensitive i.e lower/uppercase while matching.

<: Input Redirection that redirects the input i.e SampleFile.txt to the “tr” command.

tr: Represents the “translate” command that deletes/translates characters.

The description of each parameter in the above command is written here: This command is going to show ALL of the email addresses listed within the files inside a specific folder.$ tr '' '' < SampleFile.txt | grep -i -c Linux We are going to include a bonus command which is going to allow us to demonstrate how powerful ' grep' truly is: grep-tutorial]# grep -irh regular expressions we have between the quotation marks attempts to capture the pattern email addresses use, which is.

Grep while greping for grep as you grep for grep In the next example, we are going to use the ' $' regex, instructing the command to show us ONLY the lines that END with the word ' grep'. In the example above, we have used the ' ^' regex, which instructs the command to show ONLY the lines that START with the pattern ' grep'. To allow ' grep' to recognize regular expressions, you must put the ' -e' flag. These are specific characters or sequence of characters that have a special meaning within search patterns allow you to achieve a more precise result. The last example we are going to give is regarding regular expressions. This functionality can be achieved with the ' v' flag: grep-tutorial]# grep -v 'grep' test5ĭespite the fact that ' grep' happens to be stored on the previous lines, it is excluded from the output. The grep utility is also going to allow you to remove the pattern from the output completely, making it print out the lines in which the pattern is not present. You are going to see an empty output because ' gre' does not match perfectly with anything written in the files. However, when we add the ' w' option, here is what happens: grep-tutorial]# grep -iw 'gre' test5 In this case, ' grep' prints out the lines, as the ' gre' is a part of the word. grep-tutorial]# grep -i 'gre' test5 I am a grep ninja It is going to enable ' grep' to print a match ONLY if the pattern matches correctly. grep-tutorial]# grep -ci 'grep' test5Īnother useful option of the grep is the ' w' flag. To do this, we are going to be using the ' c' flag, which stands for ' count', and it is going to show us exactly what we need. Using grep, you can find the number of lines in which the pattern is present. Grep while greping for grep as you grep for grep. To demonstrate the other functions of grep, we created a new file ' text5' with the following content: grep-tutorial]# cat test5 This modification is going to generate a list of the file/s containing this specific word. To do so, replace the ' o' option with the ' l' flag. Ok, let print out only the file, which contains the pattern ' ninja' without the actual string.

o - This option allows you to print only the word you are searching for within a file, excluding the rest of the words.i - This flag allows you to ignore letter capitalization and find patterns, despite there being a capital letter inside them.It allows you to search within the folders located in the directory if such exist. To do that, we are going to use a few flags for our grep command which we are going to explain: grep-tutorial]# grep -ri 'ninja'Īs you can see, the command displayed the file along with the word ' ninja'. Let's say we need to find the pattern ' ninja' inside the files within this directory without having to open all of them one by one. Test2 - Mar 12 14:35:01 ger1 systemd: Started Session c338992 of user root. The content of these files is as follows: test1 - I am a grep ninja We have 4 test files inside the directory we are currently residing: -rw-r-r- 1 root root 10 Mar 12 14:43 test1

If you want to search through all of the files inside a directory, you do not need to define a file - just run the command as: grep The syntax of the command itself looks like this: grep We are going to teach you the standard practices you may use in your journey to master it and become a ' grep' ninja! As the possibilities this command offers are practically limitless, we cannot cover all of them in this article. It is useful when you are looking through log files, searching for a specific entry, or you want to find a unique line or piece of code located somewhere in your files. The command's primary purpose is searching for a specific pattern that can be either an integer, a string, or a combination of both and printing out the result. The ' global regular expression print' or ' grep' for short is a text processing editor.

Grep command in linux