SHELL

add line at beginning of file unix

sed -i '1s/^/your text
/' file #Note the addition of the "
" for concluding the new line after the insertion

bash append to end of line in file

# Save suffixed file into a new file
sed -e 's/^/suffix/' file > file.new

# Edit file and overwrite with suffixed text
sed -i -e 's/^/suffix/' file

add line to beginning of file shell script

$ sed -i '1s/^/added text /' file