What we don’t always know is if one or more occurrences of the word are using capitals. Now that we have performed a basic grep command, we can start to change its behavior. Often we already know the word or words we are looking for. These files can be found in your home directory. Otherwise, add it to the respective profile file. bashrc file if you are using the bash shell. As this would mean you have to type it in each time, using an alias would save you from a lot of typing. If the command above did not show colored output on your system, you might want to enable that. If you would like to find the root user in your /etc/passwd file, just tell it to search for ‘root’ and the file name itself. 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?.

Note ls -quoting-style= is not portable, stat is not portable, date -d is not portable.

# in Bash, GNU ls requiredĮval 'files=($(ls -t -quoting-style=shell-always))' After you get the filename, use stat to get the date you need, preferably as seconds since Epoch. This answer provides reliable ways to identify the most recent file in the current working directory (it seems this is what you're trying to do). In general you need LC_TIME=C ls … in the first place.īut you shouldn't parse ls in the zeroth place, at least not without -quoting-style=shell-always (which may or may not be supported by your ls) to get filename(s) (not date(s)). formatedate=$(date -d '$filedate' +%Y%m%d)īut date -d may not understand what $filedate expands to.

Bash grep extra opperand