Use the short notation in your daily tasks and on the command line, to save on typing and speed up your work. Use the long format when using them in scripts, so that it becomes obvious what the grep command is doing. The long format has two dashes, followed by a word or words. The options that grep uses typically have a long and short format. The syntax of grep consists of four parts. The grep utility does not need much to starts doing its work. Need a particular job to be done with the grep command and can’t get it to work? Use the comments and share what you have tried. Let’s start with the basics and become a ‘grep master’.īasic usage examples of grep Use grep for simple actions You can easily find out what version you have with grep -version. Some things in this guide may not be working, or need specific tailoring. If you are using grep on another platform than Linux, you may not have the GNU version of grep. Especially if you have to deal often with data, investing some time in doing things efficiently will pay off. And we will include specific use-cases which are common for system administrators and security professionals. Although these sources are a great reference, we will be showing the grep command by example. The man page is very extensive, so is the online help documentation. Why learn the grep command and regular expressions?Īs with every tool, it is often easy to start using it, but hard to really master it. It is common to use it for checking configuration files and searching through log files. We want to leverage the full potential of the grep command, as it can be used in many work-related or personal related activities. But with all information scattered, most people don’t take the time to really learn the most basic commands. One of the reasons to create this blog post is that there are a lot of examples available for the grep command. Searching inside compressed data (avoid using gunzip!).Find lines ending with a specific string.Find lines starting with a specific string.Recursive search through directories and files.Why learn the grep command and regular expressions?.In case of replacing white space with no white space do the following sed 's/ //'. First use command sed followed by 's/' and after the forward slash place the symbol that needs to be replaced, 'sed/A/a/' and right after place the other symbol that replaces the capital A. It can be anything from white space, upper/lower case letters, numbers, words, symbols etc. The sed command is used to replace parts of the data. The -d stands for 'delimited', use cut -help in the console for more options. There are several ways of using the cut tool, but the most useful I found is the cut -d method. The cut command is used (as the word says) to cut/skip the data from a particular point and keep the rest or a portion of the data. The egrep -o stands for 'all that matches'. On the script I have used egrep and egrep -o. Type egrep -help on terminal on kali linux and check for more options. The egrep command fetches the part of the data that matches with what is specified inside quotes. Then you can save it as a text file to be used later to fetch the data.

The curl command is used to retrive URL's, and html tags.

Grep examples in bash script