Using sed to add a newline on Mac OS X

As a quick note today, I have been converting parts of the Scala Cookbook from a plain text format to a Markdown format, and as part of that I needed to add some newline characters to add spacing to the document. This wouldn’t be bad if it was a few pages, but it’s hundreds of pages, so I decided to use the Unix sed command to do the work.

How to use the Linux sed command to edit many files in place (and make a backup copy)

Warning: The following sed commands are very powerful, so you can modify a lot of files successfully — or really screw things up — all in one command. :)

Yesterday I ran into a situation where I had to edit over 250,000 files, and with that I also thought, "I need to remember how to use the Unix/Linux sed command." I knew what editing commands I wanted to run -- a series of simple find/replace commands -- but my bigger problem was how to edit that many files in place.

Use sed to modify files in place

sed command FAQ: How can I use the Unix/Linux sed command to edit (modify) files in place?

The short answer is that you just need to use the -i or --in-place sed arguments, as shown in the sed man page:

-i[SUFFIX], --in-place[=SUFFIX]

edit files in place (makes backup if extension supplied)

Then, if you have a file named 'hello.txt' with contents like this:

jello, world
this is a test

you can then run a sed command like this to modify that file:

How to run a sed command from the Linux command line

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:

Unix `sed` examples: how to insert text before and after existing lines

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.)

sed swap command examples

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.

A Bourne shell script that loops through all files in the current directory

Linux shell script for loop FAQ: Can you share an example of a Linux shell script for loop, for instance, to do something for every file in the current directory?

Here's a shell script that you'll find on all the Unix, Linux, and Mac OS X computers I've worked on. The general process of this script is "for every file in the current directory do XYZ".

Linux sed command - use sed and wc to count leading blanks in a file

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)?