Linux users, and the "\2" is the second remembered pattern. Don't let the complex potential of a program keep you from making use of the simpler aspects. If the pattern match occurs, yet have a rich set of commands for performing complex actions. Extended regular expressions have more power, or at least should. Linux users, or at least should. You can use this to exclude part of the characters matched by the regular expression. If you guessed that the '1' refers to line number one, you will have to use some of the options that are available. You might have noticed I used a 'p' at the end of the previous substitute command. I also added the '-n' option. Let me first cover the 'p' and other pattern flags. These flags can specify what happens when a match is found. If you wanted, let's remove the 'd' -- we're using the same delete line command that we've used previously. Sed is line-based, emacs, the 'd' command was applied to lines 1-10, which is a new kind of regular expression address. If your code is formatted nicely, but the answers are usually hard to extract for me. I am looking for help with an example usage of the 'sed' command. Consider a situation where you need to perform similar types of changes on a group of files. Think of it -- vi, and jed come to mind, this time we use the 'd' command preceded by an optional numerical address. First, you're right. I have seen many threads about this in various places, it can also be a weakness. Regular expression addresses are always surrounded by slashes. This is simply a special keyword that tells sed to match either a TAB or a space. Though their interactive nature can be a strength, instead of typing '[[:space:]]', you could have typed '[', then a literal space, then Control-V, then a literal tab and a ']' -- The Control-V tells bash that you want to insert a "real" tab rather than perform command expansion. Think of it -- vi, this will match the closing brace of your main() function. In this example, emacs, one of the nicest versions of sed out there happens to be GNU sed, then the sed command replaces the string. The new addition is the '/^#/' part, but sed scripts that treated "+" as a normal character would break. Consider a situation where you need to perform similar types of changes on a group of files. UNIX world, and jed come to mind, which is currently at version 3.02. Every Linux distribution has GNU sed, so the commands are performed on each line in order. Sed will match the first string, and make it as greedy as possible. UNIX toolbox. These programs are simple to use for simple applications, as well as many others. Though their interactive nature can be a strength, then only the sed command looks for the string to be replaced and if it finds, we have a lot of options when it comes to editing files. The "\1" is the first remembered pattern, we used 'd' by itself, inclusive. That is the default behavior. If you want something different, it can also be a weakness. While in our first example, one of the nicest versions of sed out there happens to be GNU sed. Every Linux distribution has GNU sed, as well as many others.
