Command to change permissions only on files not directories

find . -type f -exec chmod 644 {} \;

or

find . -type f -print0 | xargs -0 -I {} chmod 644 {}`

Making functions and alias in bashrc or bash_profile

alias my_alias="command"

myfunction () {
    echo "this is my function"
    echo "This is the function with positional argument $1"
}