tee - divert stdin to a file
tee [-ai] file ...
-a Append to the files, rather than overwriting
-i Ignore interrupts
cat file1 file2 | tee x
# Save and display two files
pr file | tee x | lpr
# Save the output of pr on x
Tee copies stdin to standard output. It also makes copies on all the
files listed as arguments.
cat(1).