How to implement a condition in bash where one of two commands or conditions is executed?

In bash, to execute one of two commands or conditions, you can use the logical operators || (OR) and && (AND). To execute one of two commands if the first fails, use ||:

command1 || command2

This means: execute command1, and if it ends with an error (return code not 0), then execute command2.

If you want to execute a command when both conditions are true, use &&:

command1 && command2

For more complex conditions, you can use the if construct:

if command1; then
    echo "Command 1 succeeded"
else
    echo "Command 1 failed, executing command 2"
    command2
fi

Thus, to choose one of two commands depending on the result of the first, it is convenient to use || or the conditional operator if.