Multiple commands in an alias for bash

Question

Try:

alias lock='gnome-screensaver; gnome-screensaver-command --lock'

or

lock() {
    gnome-screensaver
    gnome-screensaver-command --lock
}

in your .bashrc

The second solution allows you to use arguments.

The other answers answer the question adequately, but your example looks like the second command depends on the first one being exiting successfully. You may want to try a short-circuit evaluation in your alias:

alias lock='gnome-screensaver && gnome-screensaver-command --lock'

Now the second command will not even be attempted unless the first one is successful. A better description of short-circuit evaluation is described in this SO question.

Aliases are meant for aliasing command names. Anything beyond that should be done with functions.

alias ll='ls -l' # The ll command is an alias for ls -l

Aliases are names that are still associated with the original name. ll is just a slightly specific kind of ls.

d() {
    if exists colordiff; then
        colordiff -ur "$@"
    elif exists diff; then
        diff -ur "$@"
    elif exists comm; then
        comm -3 "$1" "$2"
    fi | less
}

A function is a new command that has internal logic. It isn't simply a rename of another command. It does internal operations.

Technically, aliases in the Bash shell language are so limited in capabilities that they are extremely ill suited for anything that involves more than a single command. Use them for making a small mutation of a single command, nothing more.

Since the intention is to create a new command that performs an operation which internally will resolve in other commands, the only correct answer is to use a function here:

lock() {
    gnome-screensaver
    gnome-screensaver-command --lock
}

Usage of aliases in a scenario like this runs into a lot of issues. Contrary to functions, which are executed as commands, aliases are expanded into the current command, which will lead to very unexpected issues when combining this alias "command" with other commands. They also don't work in scripts.

Does this not work?

alias whatever='gnome-screensaver ; gnome-screensaver-command --lock'

This would run the 2 commands one after another:

alias lock='gnome-screensaver ; gnome-screensaver-command --lock'

Add this function to your ~/.bashrc and restart your terminal or run source ~/.bashrc

function lock() {
    gnome-screensaver
    gnome-screensaver-command --lock
}

This way these two commands will run whenever you enter lock in your terminal.

In your specific case creating an alias may work, but I don't recommend it. Intuitively we would think the value of an alias would run the same as if you entered the value in the terminal. However that's not the case:

The rules concerning the definition and use of aliases are somewhat confusing.

and

For almost every purpose, shell functions are preferred over aliases.

So don't use an alias unless you have to. https://ss64.com/bash/alias.html

So use a semi-colon:

alias lock='gnome-screensaver; gnome-screen-saver-command --lock'

This doesn't work well if you want to supply arguments to the first command. Alternatively, create a trivial script in your $HOME/bin directory.