Redirection quirks: 2>&1 >file -- vs. -- >file 2>&1

[Fred Fish]

In article <649 at watmath.UUCP> idallen at watmath.UUCP writes:
>Consider:
>
>    $ command 2>&1 >file
>    $ command >file 2>&1
>
>These are not equivalent using our 4.2bsd Bourne shell.  (The 2>&1 in the
>first line redirects unit 2 to the tty, not to the file.)

As I'm sure many others will point out, the action is entirely reasonable.
Arguments are processed as found, so in the first command, 2>&1 says
to send 2's stuff to wherever 1 is going.  Since both are probably already
going to the tty, it is effectively a no-operation.  The later >file then
sends 1's stuff off to "file".  In the second command, by the time 2>&1 is
processed, 1 is already going to "file", so 2 goes there too.

-Fred

-- 

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Fred Fish  (415) 644-1230 ext 242  ucbvax!unisoft!fnf  well!fnf
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