I prefer to do my sh commands in shorthand, And I prefer to be in POSIX.  Truthfully, if the script can run on Dash, that is good enough.  Which means using the test command [, not the extended [[.I have an example from an autostart script, which I'm not sure about.if which dbus-launch >/dev/null && test -z $DBUS_SESSION_BUS_ADDRESS; then   eval `dbus-launch --sh-syntax --exit-with-session`fiSo my guess is that if dbus-launch and $DBUS_SESSION_BUS_ADDRESS is empty, then do the eval.How do I write this in shorthand?   I appreciate any help on this subject.
POSIX and Bash, sh shorthand, for compound if statement
bash;shell;posix;dash
The snippet you posted is POSIX-legal and should run fine on dash as is.  I don't understand the point of expunging ifs and replacing them with one-liners, as it doesn't actually accomplish much besides occasionally making code harder to read.  Nevertheless, in this case, since it's just a single line, you can simply delete the if, ; then, and fi and replace the ; then with a &&, i.e.which dbus-launch >/dev/null && test -z $DBUS_SESSION_BUS_ADDRESS && eval `dbus-launch --sh-syntax --exit-with-session`should be functionally equivalent to the snippet in the question.  Also, if this is what you mean by shorthand, I don't think it's a universal or standard term and it doesn't save too many characters of typing.  Converting an if compound command to a list would be a more accurate description.