write a command

How can I arrange to have output go two places at once,
e.g. to the screen and to a file? give a command for this?

cat | cat > file will result in input going to stdout as well as filenamed file

dear gold berg just try it the command you have written on shell is it working .........
if you have not understand the question please ask me..........

Sorry I misinterpreted the question
I will try it if possible
Actually what I wrote will first ask me for Input(simultaneously write it to screen) and then just copy what I wrote to the file
(Please Correct me if I am still wrong)

Suppose u wish to see the output of 'who'
who | tee file

who|tee file1 file2> /dev/tty