Sed – Replacing a String by a File Using Sed

sed

Lets say i have two files foo and bar. I want a replace the string "this is test" in foo with the contents of the file bar. How can i do this using a one liner sed?

I have used: 

sed -i.bak 's/this is test/$(cat bar)\n/g' foo

but the the string is being replaced by literal $(cat bar) rather than the contents of bar. I have tried using quotations but the result remains the same.

Radu's answer is correct as far as the quote is concerned. Now the problem is lets say my bar file contains:

this
is
a
test
file

Now if i run the command it gives an error:

sed: -e expression #1, char 9: unterminated `s' command

18 times.

Best Answer

The following command should work for what you want:

sed "s/this is test/$(cat bar)/" foo

If foo contain more then one line, then you can use:

sed "s/this is test/$(sed -e 's/[\&/]/\\&/g' -e 's/$/\\n/' bar | tr -d '\n')/" foo

or:

sed -e '/this is a test/{r bar' -e 'd}' foo

Source of the last two commands: Substitute pattern within a file with the content of other file

To make the change in foo file, use sed -i.

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