std in, std out, std err

DEVICE=`dialog --inputbox "Festplatten-Laufzeit auslesen. Gebe Sie das

gewünschte Device an: " 0 70 "" 3>&1 1>&2 2>&3`

What is

3>&1 1>&2 2>&3

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The numbers are file descriptors and only the first three (starting with zero) have a standardized meaning:

0 - stdin

1 - stdout

2 - stderr

So each of these numbers in your command refer to a file descriptor. You can either redirect a file descriptor to a file with > or redirect it to another file descriptor with >&

The 3>&1 in your command line will create a new file descriptor and redirect it to 1 which is STDOUT. Now 1>&2 will redirect the file descriptor 1 to STDERR and 2>&3 will redirect file descriptor 2 to 3 which is STDOUT.

So basically you switched STDOUT and STDERR, these are the steps:

Create a new fd 3 and point it to the fd 1

Redirect file descriptor 1 to file descriptor 2. If we wouldn't have saved the file descriptor in 3 we would lose the target.

Redirect file descriptor 2 to file descriptor 3. Now file descriptors one and two are switched.

Now if the program prints something to the file descriptor 1, it will be printed to the file descriptor 2 and vice versa.