[arek2]

All right, but he wrote: "The 2>&1 > /dev/null puts both output stream and error stream to /dev/null (which means nothing printed on console).". So the intention was different.

PS. I think "which" will never produce anything on stderr

[fizerkhan]

As Chris said, `2>&1 > /dev/null` will drop stdout and write stderr to stdout. If you do not want anything to printed on console, you can use it. Now only i came to know that `which` never produce the stderr. So it is enough to use `>/dev/null`.