An example on how to use sed
This post is a very short one but might be really useful. You have multiple files they all contains the same string like a parameter for config files and you would like to change it in all the files. That would take you a while if you have 100 files so here is exactly what you need in 1 simple command line using sed on Linux.
The beautiful command to use sed (it's actually the same syntax than for vim)
sed -i 's/search_for/replace_by/g' folder_*/myfile*
Another tip to extract between two line numbers with sed:
sed -n 1000,10000p file > out
You can use grep to find the line number containing a particular string:
grep -n "mystring" file