Write data to text file using bash/shell scripting

You can redirect the output of a command to a file:

cat file > copy_file

or append to it

cat file >> copy_file

If you want to write directly the command is echo ‘text’

echo 'Hello World' > file

# possibility 1:
echo "line 1" >> greetings.txt
echo "line 2" >> greetings.txt

# possibility 2:
echo "line 1
line 2" >> greetings.txt

# possibility 3:
cat <<EOT >> greetings.txt
line 1
line 2
EOT

References
https://stackoverflow.com/questions/11162406/open-and-write-data-to-text-file-using-bash-shell-scripting
https://unix.stackexchange.com/questions/77277/how-to-append-multiple-lines-to-a-file