We will learn about the sed delete (d), read (r) and write (w) commands today to round out your sed toolbox. Obviously, I won’t be covering everything about sed. I literally have a book on sed that I keep handy because there is so much to it. The major parts I am covering should help you through 99% of the cases where sed is your best option.

Soon we’ll be looking at awk and other tools to continue the quest for command-line fluency. If you haven’t already, install Cygwin and check out part 1 and part 2.

Tutorial

One of the best ways to crank out code quickly is by using templates. Using the Stream EDitor, you can streamline the use of templates.
Continue reading →

Now that you know a bit about the Stream EDitor from the last sed tutorial, we are going to expand our knowledge of substitution and line printing with an interesting scenario.

Suppose we want to let someone else know what kinds of functions are in a given Javascript file. Think of it as a simple sort of Javadoc for CSS or Javascript. The way we are going to do this is look at all of the files modified in the last day and then extract the comments out of them and put them somewhere (on a wiki perhaps?). Doing this kind of automation will increase team communication and productivity immensely if done correctly.

Tutorial

Download and install Cygwin if you’re on Windows to follow along.

[code language="bash"]
# Single-line comments - grep is better but we can use sed
sed -n '///p' blah.js > /tmp/comments.out

# Multi-line comments
sed -n '//*/,/*//p' blah.js >> /tmp/comments.out
[/code] Continue reading →

Today I’ll continue the series on command-line tools for productivity, with sed. Stream EDitor is the most complicated tool so far, an entire language in its own right. It is much too big to cover completely in one post, so I’m going to have a few posts covering the major parts of sed.

The bread and butter of sed is its search-and-replace functionality. Let’s start with that and then throw in some other fun commands.

Tutorial

As with the previous posts, if you are on Windows you’ll want to install Cygwin or one of the various other tools suggested in the previous comments. sed also uses regular expressions so you’ll want to keep your regex reference handy. From Wikipedia:

[sed] reads input files line by line (sequentially), applying the operation which has been specified via the command line (or a sed script), and then outputs the line.

[sourcecode language="bash"]
sed ‘s/#FF0000/#0000FF/g’ main.css
[/sourcecode]

We can read this like so: search [s/] for red [#FF0000/] and replace it with blue [#0000FF], globally [/g] in main.css. Two notes here: 1) This does not actually modify the file, but outputs what the file would look like if it did the replace and 2) If we left off the "g" at the end it would only replace the first occurrence. So let’s modify the file this time. Continue reading →