Command Output

Every command has an output: the answer a function doing the same thing would give. @dig outputs the new room, as dig() returns it; think outputs what it thinks. The output is never the text the command shows you. @find shows a line per object and a count, and outputs the list of objects.

The %> substitution holds the output of the last command run in the same action list, so the next command can use it:

> @force/noeval me={@dig Kitchen;think Dug [name(%>)] as [num(%>)].}
Kitchen created with room number 12.
Dug Kitchen as #12.

The examples run their lists with @force/noeval me={...}, the way to try a list at the prompt. Without /noeval, @force evaluates the list once before running it, as PennMUSH does, and every %> in it is read then, before any command has run, so it is empty.

To use what a command shows instead, pipe it into the next command with ;| and read %|: see piping.

A command that outputs something says what in its help, on a line starting Output:. Most commands that change something output nothing, and the next command replaces %>. To use a value after such a command, keep it in a q-register: @dig Kitchen;@desc [setq(0,%>)]%q0=A small kitchen.;@link %q0=here.

A command that fails leaves the #-1 error it failed with, the way its function would return it.

What each command leaves

A value. Building commands output what they made (@create, @dig, @open, @clone, @pcreate). Searches output what they found (@search, @find, @entrances, @scan, @grep, @whereis, inventory). look, examine and @decompile output the object they showed. Moving with goto, an exit, enter, leave or home outputs where you arrived. @config with one option, @sql, @uptime and @version output what config(), sql(), uptime() and version() give.
Nothing. Commands whose function returns nothing output nothing: speech and emits (say, @pemit, @emit, …), settings (@set, @lock, @link, @tel, @name, @parent, …), and administration. They clear %>.
What the list they ran left. @include, @switch, @select, @ifelse, @skip, @dolist, @map, @trigger, @force, @retry, teach and with run commands. When they run them in place (/inline, /inplace, @include), %> is the output of the last command that ran. When they queue them, nothing has run yet, and %> is cleared.
Unchanged. @@, @assert and @break leave %> as they found it, so a check in the middle of a list does not lose the value.

> @force/noeval me={@dig Pantry;@assert %>;think Still have [name(%>)].}
Pantry created with room number 13.
Still have Pantry.

Output across the queue

A queued action list (@wait, a queued @switch or @dolist, @trigger) starts with a copy of %> from when it was queued, the way it gets a copy of the q-registers. The list that queued it can go on changing its own %> without affecting it.

> @force/noeval me={think first;@wait 1=think Was %>.;think second}
first
second
Was first.

Each line typed at a connection starts with an empty %>; the output of the previous line is not kept. A function such as u() reads the %> of the list that called it. An @hook/after reads the output of the command it hooks.