So I frequently find myself in a situation where I need to modify files on a fairly programmatic basis, so sed has become a friend of mine for a lot of these situations.  So lets start with some basic sed…

If I have a file..

bash 
cat /etc/file.txt
blah
blah
teststring
blah
blah

And I want to replace “teststring” with “productionvalue” then I could use sed.

bash 
sed -i 's/teststring/productionvalue/g' /etc/file.txt
bash 
cat /etc/file.txt
blah
blah
productionvalue
blah
blah

This is all well and good, but recently I found a better way…

Using perl, not only can we make the change, but we also create a backup file of the original configuration.

bash 
perl -pi.orig -e 's/teststring/productionvalue/g' /etc/file.txt

So now lets take a look at our original file with the .orig extension…

bash 
cat /etc/file.txt.orig
blah
blah
teststring
blah
blah

And finally our changed file…

bash 
cat /etc/file.txt
blah
blah
productionvalue
blah
blah

This is certainly a more useful way of making programmatic changes while retaining the ability to quickly recover from programmatic errors…