Replace string between two words with the content of another text file

I am bit new to sed and regex.

I was trying to edit a text file, where I want to replace the contents between two keywords in the first file with the entire contents of another text file

it should like this -

keyword1 inbetweenstuff keyword2

to this

keyword1 textfromfile2 keyword2

I was trying this command, but no luck

sed -i 's/(keyword1).*(keyword2)/\1 contentsoffile2 \2/g' file1.txt

Solution

You're trying to use the wrong tool. sed is for simple substitutions on individual lines (s/old/new/), that is all. For anything more interesting you should be using awk.

With GNU awk for multi-char RS, gensub(), and the 3rd arg for match():

$ cat file1
keyword1 IN BETWEEN
STUFF ON
ONE OR MORE
LINES keyword2

$ cat file2
NOW IS
THE WINTER OF
OUR DISCONTENT

$ cat tst.awk
BEGIN { RS="^$"; ORS="" }
NR==FNR { new = gensub(/\n$/,"",""); next }
match($0,/(.*keyword1 ).*( keyword2.*)/,a) { print a[1] new a[2] }

$ awk -f tst.awk file2 file1
keyword1 NOW IS
THE WINTER OF
OUR DISCONTENT keyword2

Note that the above treats the contents of file2 as a literal string so the contents of "file2" can be anything. Try any of the sed solutions if "file2" contains an &, for example (or \1 or / or ...). It also doesn't care how many lines are in file2 or how many lines are between the keywords in file1.