Unix shells commonly provide several forms of redirection---ways to change the input source or output destination of a command. But one useful redirection is performed by a separate command, not by the shell; it's described here.
tee
: Redirect output to multiple files
The tee
command copies standard input to standard output and also
to any files given as arguments. This is useful when you want not only
to send some data down a pipe, but also to save a copy.
Synopsis:
tee [ option ]... [ file ]...
If a file being written to does not already exist, it is created. If a
file being written to already exists, the data it previously contained
is overwritten unless the -a
option is used.
The program accepts the following options. Also see section Common options.