Practical sed commands

I am posting a summary of my  commands after a bit of Googling and after playing on my CentOS VM with sed.

1. Always backup your files before playing with sed

2.The -i option in sed will replace the original file. So I recommend you run your
sed commands without the -i option first. Once you get the desired results of your sed command you
can then use the -i option.

append after <body>

sed  '/<body>/a Hello World' sample.html
sed -i  '/<body>/a Hello World' sample.html

append contents of file header-js.txt after <body>

sed -i '/<body>/ r header-js.txt' sample.html
sed -i '/<\/body>/ r footer-js.txt' sample.html

Some tests before proceeding further (tip: don't ignore the single quote)

[root@localhost mydir]# find . -name '*.html'

combine find with sed for mass modifications

find . -iname '*.html' -exec sed -i '/<body>/ r header-js.txt' '{}' \;
find . -iname '*.html' -exec sed -i '/<\/body>/ r footer-js.txt' '{}' \;

append at beginning of file

sed -i '1s/^/my script goes here\n/' file