sed

Yesterday I ran into a situation where I had to edit 250,000 files, and of course I instantly thought of the Unix/Linux sed command. I knew what edit commands I wanted to run (simple swap/replace commands), but my bigger problem was how to edit the files in place.

A quick look at the sed man page showed that I needed to use the -i argument of the sed command:

Linux sed FAQ: How do I run a Linux sed command from the command line?

I usually only use the Linux sed command in sed scripts, but today I needed to do something much easier than normal, and as I thought about how to run a sed command from the Linux command line, I had to pause for a few moments. Finally I remembered the sed command line syntax, and it looks like this:

sed 's/THE_DATE/2010-07-11/' < sitemap-orig.xml > sitemap.xml

This sed command can be read like this:

If you ever need to use the Unix/Linux sed command to insert text before or after a line of text in an existing file, here's how I just ran several sed commands to update my old Function Point Analysis tutorial to have a format that doesn't look like it was created in the 1990s.

This tutorial consists of over 40 files, and I had eight changes I wanted to make each file. So I had two choices: modify each file by hand over the next six hours, or run a series of sed commands and be done in 30 minutes. (I chose the sed commands.)

Summary: This post shares some Unix/Linux sed command swap/replace examples, where you replace one string or regular expression with another string.

Here's the source code for a sed script that I used to convert some poorly formatted HTML into a format that I preferred. I ran this on a set of almost 30 JSP files from an open source project I recently worked on. The good news is that the previous format of the files was consistent, so I was able to use this sed script to convert all the files at once.

I use JSPs and servlets to generate a lot of the pages around here, and today I looked at how many blank spaces and blank lines are generated by the JSP's. I don't think I can do much about the blank lines (actually, I just haven't looked into it yet), but about those blanks spaces ...

Out of curiosity I decided to look at this -- how many blank spaces are there at the beginning of lines that I could delete just through formatting? Would deleting those characters help reduce my bandwidth costs (at the expense of slightly uglier JSP's)?