Replacing one line in text file with line from other file

[abraxas334]

I have a question regarding replacing line in files.
I want to replace the ith line of replace.dat with the jth line of othertext.dat how can i achieve this?

[Vaphell]

i=2; j=2
sed "${i}s/.*/$( sed -n ${j}p overtext.txt)/" replace.dat

you can plug numbers directly in ${i} and ${j}'s place
by default sed prints to screen, if you want to save the changes either redirect output to new file with > output.file (non-destructive=safer) or with -i parameter given to main sed command (overwrites source file, so better be sure it works first)

[ofnuts]

head -$((i-1)) replace.dat > out.dat
head -$j othertext.dat | tail -1 >>out.dat
tail -n +$((i+1)) replace.dat >>out.dat

[abraxas334]

Thanks for all the replies! This helped alot!