I needed to generate a .htaccess redirect file where each line has a simple command

redirect 301 old-file new-file

The file called crawl-error.txt with all the required urls that needed a redirect was quite long so I did the following in no time. First ensure that the file is really a proper text file as otherwise whatever you want to append will be prepended instead.

dos2unix crawl-error.txt

Then prepend the text, in my case “redirect 301 “, and output the result to .htaccess

awk '{print "redirect 301 " $0}' crawl-error.txt > .htaccess

then append the required text, in my case ‘http://www.travellers-palm.com’

sed -i "s|$| http://www.travellers-palm.com|" .htaccess

Voila that was all.