Is it possible to pass passwords on a shell script?

By "entering passwords", you likely mean entering data without being visible for the user.

(suggested by geirha) When using bash, you can use the -s option to prevent typed characters from being displayed:

read -p "Password please: " -s pass

Alternatively, change the behavior of the terminal to hide typed characters with stty -echo (disable echo). After reading the password with the shell built-in read into a variable (in the below example, $pass), turn it back on with stty echo. Because the new line from Enter is hidden to, you've to print a newline to get future output on a new line.

stty -echo
read -p "Password please: " pass
stty echo
printf '\n'

read and printf are shell built-ins. stty is provided by the coreutils package which is installed by default. That means that this snippet is very portable.

Note: the -p option is not standard, but from bash. If you need to display a prompt in other shells, use:

printf "Password please: "
stty -echo
read pass
stty echo
printf '\n'

References:

• Manual page of stty
• Manual page of bash

To which program do you want to pass a password?

The script on the link works for me. Note that is not a shell script but an expect script (needs the package expect to be installed`). Using expect is a common way to automate text based interactive programs.

Non-interactive ssh logins are often done using key-based authentication with an empty passphrase.

Some other programs (like sudo) have options to read a password from stdin.

Providing a password as a command line option is often a security problem as on most systems any user can see any other users processes including there command line arguments using simple tools like ps.