Is there a way to ignore header lines in a UNIX sort?

I have a fixed-width-field file which I'm trying to sort using the UNIX (Cygwin, in my case) sort utility.

The problem is there is a two-line header at the top of the file which is being sorted to the bottom of the file (as each header line begins with a colon).

Is there a way to tell sort either "pass the first two lines across unsorted" or to specify an ordering which sorts the colon lines to the top - the remaining lines are always start with a 6-digit numeric (which is actually the key I'm sorting on) if that helps.

Example:

:0:12345
:1:6:2:3:8:4:2
010005TSTDOG_FOOD01
500123TSTMY_RADAR00
222334NOTALINEOUT01
477821USASHUTTLES21
325611LVEANOTHERS00

should sort to:

:0:12345
:1:6:2:3:8:4:2
010005TSTDOG_FOOD01
222334NOTALINEOUT01
325611LVEANOTHERS00
477821USASHUTTLES21
500123TSTMY_RADAR00

Solution 1:

(head -n 2 <file> && tail -n +3 <file> | sort) > newfile

The parentheses create a subshell, wrapping up the stdout so you can pipe it or redirect it as if it had come from a single command.

Solution 2:

If you don't mind using awk, you can take advantage of awk's built-in pipe abilities

eg.

extract_data | awk 'NR<3{print $0;next}{print $0| "sort -r"}' 

This prints the first two lines verbatim and pipes the rest through sort.

Note that this has the very specific advantage of being able to selectively sort parts of a piped input. all the other methods suggested will only sort plain files which can be read multiple times. This works on anything.