Introduction
We will be most concerned with GNU Sed (it seems to be version that offers more features (GNU extensions vs POSIX). Still, we’ll try, whenever possible, to offer versions of the examples that work in a more portable way.
Read Sed’s info and man page. The info page is much more verbose, while the man page is more concise. In my opinion, although the info page is much more beginner friendly (and I dare to say that the man page even lacks important information), both are hard for a Sed neophyte to get started.
Info page:
info sed
The info page can also be read online here.
Man page:
man 1 sed
It is a good idea to read the man and info pages entirely at least once to get a feel for what commands, options and features are available. Don’t worry if you don’t understand some or most of the parts. We are going to refer back to specific documentation as we go along when necessary.
In OpenBSD, both the info page actually opens the man page. As mentioned earlier, the info page is more detailed. Keep in mind, however, that OpenBSD is famous for its precise, correct and up to date documentation (among other qualities, of course). Sed’s online manual page is found here.
A Note About Shells
Sed is used from a shell, or in combination with some other command line tool or shell feature. Most of the examples were tested on Bash because it is the default on the majority of Linux systems. We assume that most examples will also work on Zsh, Ksh, and other modern shells or can be easily modified to work on those shells (at least after a quick web search, asking on the shell’s mailing list or their IRC channel). BSD users are generally savvy enough when it comes to shell and command line so we’ll assume they can tweak the examples to make them work on those systems ans shells as well.