Sed
From FreeBSDwiki
Short for "Streamline Editor", sed allows you to run a file through it and either match or change data without actually editing the file itself.
The most common usage is to change all instances of a phrase to another; to wit:
dave@samizdata:~% cat sed_testfile dave dave davedave jimbo dave freebsd dave@samizdata:~% sed s/dave/david/ sed_testfile david david daviddave jimbo david freebsd dave@samizdata:~% more sed_testfile dave dave davedave jimbo dave freebsd dave@samizdata:~%
As you can see, the changes were not actually made to the file. I didn't tell it to put the changes anywhere! Easily fixed with the help of redirection:
dave@samizdata:~% sed s/dave/david/ sed_testfile > sed_testfile_new dave@samizdata:~% more sed_testfile_new david david daviddave jimbo david freebsd dave@samizdata:~%
