Question

5

Delete multiple lines from file when text is found

rated 0 times [ 5] [ 0] / answers: 1 / hits: 15594 / 2 Years ago, sun, october 9, 2022, 5:14:07

I've seen multiple answers to delete a single line with sed or grep, but I'm in need to search for a line, delete that one, and the 2 proceeding lines. For example, in the file ~/.profile I have lines like:

#Set environment variable

export NAME=value

# (blank line here)

So I'd like to search for #Set environment variable, and delete it, then delete the next line export NAME=variable (content shouldn't matter), and the following blank line. The export variable names are dynamic, but the comment will always be the same. There could be other export variables without the above comment which I do not want to delete.

How can I accomplish this?

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moloy

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2 Years ago

answered 2 Years ago mugustered · Accepted Answer

With the newer version of GNU sed (comes with Ubuntu), you can match the newlines literally:

sed -z 's/#Set environment variable

export [^

]+



//g' file.txt

-z option will treat the lines of input files as terminated by ASCII NUL rather than newline, thus we can use to match the new lines

#Set environment variable will match the first line (with new line)

export [^ ]+ will match the second line starting with export

As the third line is blank simply will do

Then we replace the whole pattern matched with blank to keep the desired portion

In you want to overwrite the file with the modified content:

sed -zi.bak 's/#Set environment variable

export [^

]+



//g' file.txt

The original file will be retained as file.txt.bak, if you don't want that just use sed -zi.

Here is a test:

$ cat file.txt 

#Set environment variable

export NAME=value

#some text



#Set environment variable

export NAME=value



check

value



export some=value



#Set environment variable

export NAME=value



foo bar







$ sed -z 's/#Set environment variable

export [^

]+



//g' file.txt 

#Set environment variable

export NAME=value

#some text



check

value



export some=value



foo bar