On Sun, Apr 14, 2002 at 10:48:43AM -0700, Wolfgang Pfeiffer wrote:
> Hi,
> and thanks for your fast responses :)
> --- [EMAIL PROTECTED] wrote:
> > On Sun, 14 Apr 2002, Wolfgang Pfeiffer wrote:
> > > But could someone explain in human understandable words, what
> > > this part exactly means?
> > It redirects both "stdout" (standard out) and "stderr" (standard error) to
> > the file /dev/null which is "never never land".
> I don't see the connector between '> /dev/null' and '2>&1' ...
> For example:
> cat /dev/null > some_file
> means - if I understood it correctly - that the system reads
> '/dev/null' and writes it to 'some_file' with a little help
> from '>', which I call here the connector between both
> parts of them. --- But what is the connection between
> /dev/null' and '2>&1'
Yeah, you got two answers that were the same and both were
correction and neither gave you the details or really answered your
question... Ok... Let me give it a try...
... > /dev/null 2>&1
Means, literally...
Redirect stdout (File Descriptor (fd) #1) to /dev/null [ > /dev/null ]
= THEN =
Redirect stderr (File Descriptor (fd) #2) to fd #1 [ 2>&1 ]
The 2>&1 construct maps file descriptor #2 [ 2> ] over file descriptor
number 1 [ &1 ] so that were ever file descriptor #1 is being directed
to, that where file descriptor #2 output will also be directed (/dev/null
in this case). It can be generalized... n> means redirect fd #n. It
can be redirected to a file or to another file descriptor. &m is then the
notation for the file descriptor which is the target of the redirection.
So 2>&1 dumps the output on file descriptor 2 onto file descriptor 1.
0 is stdin, 1 is stdout, 2 is stderr, and you can use higher descriptors
if your application understands them (useful in perl scripts).
Note, however, that this is a mapping and that order is important!
"2>&1 > /dev/null" will map the stderr to what stdout USE TO BE, then
map stdout to /dev/null. That probably won't do what you want and certainly
does NOT do what's above (unless stdout was aleady directed to /dev/null).
> Thanks in anticipation
> Wolfgang
Mike
--
Michael H. Warfield | (770) 985-6132 | [EMAIL PROTECTED]
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