2>&1

A common practice when adding entries to crontab is to end the entry like this:

 >/dev/null 2>&1

The purpose of this is to suppress any output from the command itself, because we’re not interested. I picked up this syntax years ago because it just works, but I never knew what the ‘2>&1′ actually meant, until today.

The first part:

 >/dev/null

Means redirect STDOUT (the standard output stream) to /dev/null (which is basically a blackhole for bits). That’s easy enough.

The second part:

 2>&1

Means redirect STDERR (standard error stream) to the same place as STDOUT (which was just specified). STDOUT has the assigned number 1 and STDERR has the assigned number 2.

This way both STDOUT (1) and STDERR (2) are directed to /dev/null and all output of the cronned command is suppressed.