sed . . . the stream editor
Find here the sed FAQ (Frequently Asked Questions) file, some one-line sed scripts, and a brief introduction to sed. I suggest several "flavors" of sed for DOS/Windows users.
What is sed?
Originally designed for Unix, sed has been available for DOS and other operating systems for many years. Sed is a non-interactive editor that works from a command line; it is not a Windows application with icons or a menu bar. What does it do? sed changes text: deleting, adding, inserting, substituting.
Sed changes blocks of text "on the fly" by using a pre-written
list of commands. With sed, you don't open up a screen, push a cursor
around, and press DELETE or INSERT or
various function keys.
"Hey," you might ask. "Is it just a find-and-replace program? You can find that in any word processor."
Not like this. Sed is very powerful, and you can do things in sed you can't do in any standard word processor, even ones that support "regular expressions". Also, because sed is small and works on a "stream" of text, it can quickly alter files several gigabytes in size.
How it works: You feed sed a script of editing commands (like, "change
every line that begins with a colon to such-and-such") and sed sends the
altered text to the screen. To save the revisions on disk, use the
redirection arrow, >newfile.txt
This sample will change "black" to "white" throughout your file:
sed "s/black/white/g" input.txt >output.txt
This sample shows how to make sed read a multi-line sed script, myscript.sed, instead of entering multiple commands from the command prompt:
sed -f myscript.sed input.txt >output.txt
Setting up an environment for sed
Since I expect that most of the visitors to this page will be people who (like me) work in a DOS/Windows environment, I am writing a separate document to explain the effective use of the Command prompt. Read it to avoid frustration and wasted effort on the command prompt.
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