For convenience, I'll define the prompt and command first:
set prompt "date" ;# our remote command set prompt "% " ;# our shell or whatever prompt we have
Now we can do useful things:
expect "$prompt" ;# wait for prompt send "date\r" ;# send command expect "$prompt\r\n" ;# discard command echo
Finally, match and save the result and discard the next prompt:
expect -re (.*)\r\n$prompt\r\n"
Now the result is in $expect_out(1,string).
If you want to read more about this, start on page 113 of BOOK Exploring Expect. This idiom is difficult for some programmers; the point is that Expect never gives direct access to "the result of a (foreign) command"; it simply transacts send-expect dialogues, and one has to know how to subtract out prompts, newlines, and other conventional decorations.
PS: If the result might be more than 2000 characters, you'll need to use the match_max command to increase the buffer space.
"Remote input-output with Expect" gives a model for line-oriented result access.
The example above didn't work for me (yes, I know that the above is not a complete programme). The following is an example which works on my machine FreeBSD 4.7
set prompt ">>> " ;# our shell or whatever prompt we have set command "date" ;# the command whose ouput we want to catch
spawn bash ;# spawn the bash
expect "$prompt" ;# wait for prompt
send "date\r" ;# send command expect "date\r" ;# discard command echo
expect -re (.*)\r" ;# match and save the result