Replace text inside files with just one command: perl

On certain occasions we want to replace text within a file, for example, change in Document.txt everything that "my family" says for "us." To achieve this we can use our preferred text editor (Kate, Gedit, SublimeText, etc) but it is always good to know variants, other ways to achieve the same result 🙂

It happens that with regular expressions you can achieve this, the sed command is simply magnificent, it has endless variants and options but ... for those who just want to replace text from the least complex way possible, for them it is that I bring this much simpler variant:

Following the example, we have the file Document.txt located in $ HOME / Document.txt with the following text:

(...) my family it's like all of them, like yours or your neighbor's. In fact my family We try to be responsible people and in the eyes of society, politically and socially correct. However, in my house there is a black sheep, and that is my role LOL !. I have always been the one who is not afraid to say what he thinks (even if it is not apparently correct in the eyes of society), although in reality my family is fed up with the dirt today's society.

With the following command you will change «my family" by "Us«:

perl -pi -e "s[mi familia][nosotros]g" $HOME/Documento.txt

It's that simple 🙂

So the text would be:

(...) Us it's like all of them, like yours or your neighbor's. In fact Us We try to be responsible people and in the eyes of society, politically and socially correct. However, in my house there is a black sheep, and that is my role LOL !. I have always been the one who is not afraid to say what he thinks (even if it is not apparently correct in the eyes of society), although in reality my family is fed up with the dirt today's society.

The syntax is:

perl -pi -e "s[lo-que-quiero-cambiar][lo-nuevo-a-poner]g" archivo-en-el-cual-reemplazar

The command may seem a bit complex, let's break it down a bit and explain it a little more simply 😉

• perl : What we will use, perl
• -pi : Pí, how π (the approximate value of 3.14)
• -e : The E imagine it for «e to execute» (I.e.
• Then in quotes » we open with a s and we close with a g: "sg" … Imagine the S for Start and the G for Game Over 😀
• Turn between the sg we must put two sets of brackets: [] y [], being that way: "S [] [] g"
• Inside the first brackets as I said above, the text that we want to remove and replace with a new one will go, while in the second set of brackets the new text to put will go, following the example: "S [my family] [we] g"

Simple isn't it?

The explanation is actually much more extensive than what is necessary for the command, it is quite simple to understand 🙂

Perl is much, much more than a way to replace text, it's a whole language 😉

If you want to learn more about it, install the package perl-doc and take a look at whooodo what it allows, it's just a different universe.

By the way and to close, assuming you want to find all the .txt files you have in $ HOME / Documents / and in each one replace "my family" with "us", you can join find + perl to achieve this:

find $HOME/Documentos/ -name *.txt -exec perl -p -i -e "s[mi familia][nosotros]g" {} \;

Or using a wildcard:

perl -p -i -e "s[mi familia][nosotros]g" $HOME/Documentos/*.txt

The problem with this second variant is that it will not replace in files that are in subfolders 🙂

Anyway, I hope you found it interesting. For me it has been really useful, I can already replace text directly from the terminal ... great! 😀