Need help with SED command
 

Hi,
I have been trying to remove few lines of text in a file -



I basically want to remove the following -


I used this command

any idea where I went wrong?

Thats what I had typed. the problem is that the text still remains in the new file.

If you want to edit the file in place, use the -i option. Be careful with that: if you are not really sure that the result is exactly what you're trying to do, the loss of the original file is at risk. Anyway, you can use the -i option in the following way to do a safe backup copy:
this will create a copy of th original file, called file.bck, where .bck is just an example. Actually, you can choose the suffix at your pleasure.

I did this

I ended with a blank file u.txt and nothing in article1.txt changed :((

What could be wrong?

What's with all the escaping? I just used the following:
Of course, this only removes the first commented section. To remove the second one, you'd need to modify it. Probably the easiest way to do it is to simply address the number of lines following the first match (assuming gnu sed).
A useful way to debug a sed expression is to first set it to print only the lines you want to match first. Then once you get it working correctly, reverse it.
PS: I often use the sed faq to help me with my matching needs.

">u.text" redirects standard output to the new filename. Since you used -i to edit the original file in place, there's no output to redirect. And since the expression failed to match, there was nothing to edit in the original file either.

As David said! :)

My mistake. I didn't notice that it was space. Anyway shouldn't '<?' mean an optional '<' and not '<?' ? I haven't tested it though.

In extended regexp mode, yes. But without the -r flag, sed uses only a simplified "basic" regex syntax and "?" loses its special meaning (along with some other characters).

In fact, in basic mode, escaping the question mark actually enables the extended regex functionality!

The grep manpage goes into more detail about the differences between basic and extended regex, since it works the same way.

i see thanks for the info.

Anyone who can remember all the differences between regular and extended Regexes---AND how those differences vary among programs---is worthy of sainthood.

I have developed a simple approach: Trial and Error

I highly recommend the OWL book http://regex.info/

Indeed ... Friedl is a genius :}