bash-3.2$ exec &> >(tee -a "testlog")
bash-3.2$ echo "This will be logged to the file and to the screen"
This will be logged to the file and to the screen
bash-3.2$ uname
Darwin
bash-3.2$ nl testlog
     1  bash-3.2$ echo "This will be logged to the file and to the screen"
     2  This will be logged to the file and to the screen
     3  bash-3.2$ uname
     4  Darwin
     5  bash-3.2$ nl testlog
bash-3.2$ exit