Redirect both stdout and stderr to a file:

Redirect both stdout and stderr to a file:
# ls &> filename

Note: This operator is now functional, as of Bash 4, final release.

Redirect stderr to stdout (&1), and then redirect stdout to a file:
# ls > filename 2>&1

Note: 2>&1 redirects file descriptor 2 (stderr) to file descriptor 1 (stdout).

Reference:

https://stackoverflow.com/questions/7526971/how-to-redirect-both-stdout-and-stderr-to-a-file