Linux Tool Find Is A Swiss Army Knife Of System Administration

Okay, as stated at the fag end of the last article I wrote, I am going to write about a tool, name find. And here we are, in this post, I will try to show you the minimal use case of using the tool. It is an invaluable tool in any sysadmin’s armory. Importantly, it makes things easier for them to use other stuff efficiently.

Just a note, there is a package maintained by most of the Linux distributions, named findutils¹ and it has some other close-knit siblings in it. So, please be aware and get that package.

Generally, looking for something in the system can be done with find in a much faster way. The only impediment might be the damn syntax, especially, those flags, until you get accustomed to those. Or, you probably, automate a few of those frequently happening activities to put things inside a script and give it an apt name(this is very important, I can not stretch more the importance of having it).

Inside of the script, always … always use find instead of other tools for finding. Why? Because it has got precise things with flags that make things play well within your script.

Nope, I am writing this article NOT to show off a plethora of examples, which are littered on the internet and absolutely good for people. Here I am trying to make you understand(if you take that with a pinch of salt 🙂 ) and realize how good it will be to use a tool which stood the test of time and is still very relevant and kicking.

Because, the files are scattered in the system in various locations, due to the nature of the operating system’s requirement and the other system tools to be able to find and use, we are often left wondering about the stuff we are looking for in the system. The aid we seek in the very first place is to use find from the command line or from the comfort of the editor environment. People wrote many a thing, which wraps the find command to suit the particular editor environment they are sitting in. I think that integration with the editors makes things easy for people at least one step, that is to go out of that convenient zone and try things out at the command line and then come back.

If you are a person, who is more comfortable looking things up on the internet, than using the man command at the terminal to see the documentation then you might be interested to see this page², I love manpages that have examples.

Now, the thing is you are best served, when you use it on the command line or within a script. The precision it provides matches none other.

Alright…alright you are itching to see some examples and I am not going to disappoint you regarding that, but with a very limited set.

Finding the latest file in the directory

find $HOME/bibliography/pdf_docs/ -maxdepth 1 -type f -newermt $(date '+%F') -ls | gawk '{ print $11}' | sort -f -i -r | head -1

See! It is not just alone, but get help from other known tools (i.e. head,gawk,sort) all the way.

Find empty files

find . -type f,d -empty -print0

Here, find is instructed to find out all the empty files and directories of the specific directory, where it is fired from. That dot signifies the local directory you are sitting on. And it takes an -empty flag too. Notice, that it also directs the -type flag to have files and directories both with comma-separate flags. Lastly, it prints out the stuff without the newlines appended to the filenames.

*The difference between print and print0 is the former output with newlines* *and second one output without newline.*

Let me show you the difference visually 🙂

Find print expression with newline, this is the default

And this is the default way to find print stuff on stdin.

Find print expression without the newline aka -print0

This form is more suitable to infuse with other tools along the pipeline.

Find any specific filename extension with regex

Find dot files and use fzf to enlist them and then use vim to open the selected one

find $dir -maxdepth 1 -name ".*" -type f | fzf | xargs -I {} vim {}

That $dir variable has to hold the directory path, where you want to search. It also introduces another important flag, i.e. maxdepth , which can be a great help, if you try to maneuver with a big directory with lots of files but want to restrict the search-specific directory level.

I have mentioned that findutils package comes with bundles with other utilities too and those included are :

• locate³
• updatedb⁴
• xargs

To use locate you have to build the database first by running updatedb. People generally run this command from cron at certain intervals. Because the database has to be kept in sync with the system running it by hand doesn’t make much sense.

Here is how it can be used from the command line:

About xargs!⁵ Ah, it is the closest cousin of find and use extensively. You saw the very example just above that I have used to run Vim against the output holding of the piped command.

Let me show you three classic cases of using xargs aptly 🙂

Move files from A to B in a bunch at once

find . -name "*.bak" -print 0|xargs -0 -I file mv file ~/old

This command looks for files with specific extensions i.e.bak prints them without newline(I showed you in the above) and then piping it to xargs to move to a specific directory.

Using Sed⁶ to change something

ls |xargs -n1 -I file sed -i '/^Beg/d' file

Add file name to the first line of a file

ls |sed 's/.txt//g'|xargs -n1 -I file sed -i -e '1 i\>file\' file.txt

DON’T use file as file name literally, you have to use the actual file name

Footnotes:

^{1 GNU Findutils Package}

^{2 Online Find Man Page}

^{3 Oniine Locate Man Page}

^{4 Online Updatedb Man Page}

^{5 Online Xargs Man Page}

^{6 Online Sed Man Page}