Deleting a multiline block of text between regex pattern using sed

Question

I have a duplicated block of text I need to delete in a large xml file. I want to keep the first block and delete the second all within the same xml tag. For example:

<!--#if--> 
 -- several lines of text
<!--#else-->
-- several lines of the same text
<!--#endif-->

I'd like to delete the second block between the else and endif, and keep the keep the block between the if and else tags. Any help much appreciated - the script ends up deleting the entire file.

sed -i '/^<!--#else-->/ {p; :a; N; /^\<\!--\#endif--\>/!ba; s/*.\n//}; d' test.xml

The expected output is output everything outside the blocks and the text between #if and #else - i.e. I only want to delete the duplicate text between #else and #endif — user2167052
– user2167052, Commented Jan 5, 2015 at 8:54

aelor · Accepted Answer · 2015-01-05 09:07:38Z

4

I think this should work for you

sed '/--#else--/,/--#endif--/{//!d}' test.xml

this will delete the lines between else and endif

if you want to delete else and endif as well use this:

sed '/--#else--/,/--#endif--/d' test.xml

in the case you mentioned in the comments try this:

sed -n '/--#else--/,/--#endif--/p' test.xml

-n is dont print by default and /p does the print while /!d does the delete

edited Jan 5, 2015 at 9:07

answered Jan 5, 2015 at 8:49

aelor

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6 Comments

user2167052 Over a year ago

Thank you, I thought I had over complicated it. Running it it seems to work, but how can I capture it and output to a new file? -i.bak does not seem to work, it leaves the two files of the same size.

user2167052 Over a year ago

Damn, it's not working for me. If I just run the command above - as it scrolls you can see that the block is deleted. However if I try to output to a new file or use -i.bak I end up with two files of exactly the same size - nothing is deleted. I also tried cat test.xml | sed '/--#else--/,/--#endif--/{//!d}' > new.xml and I end up with two files of exactly the same size.

aelor Over a year ago

sed '/--#else--/,/--#endif--/{//!d}' deletes the lines doesnt output anything, use the last command I gave then you will get the result as output in your terminal then you can output it to a file using >

aelor Over a year ago

@user2167052 glad that works for you. You can mark the answer as correct if you feel your query has been resolved.

arya Over a year ago

What if you want to delete the #else but not the #endif?

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