[ale] output redirection (easy?)

Joseph A Knapka jknapka at earthlink.net
Mon Dec 3 07:36:52 EST 2001


Chris Bergeron wrote:
> 
> I have a feeling this is a simple question:
> 
> I'm trying to get the time from a command:
> time dd if=/dev/hda of=/backup/system.img > /backup/system.msg
> 
> but...  when it runs I get the output of the dd command;
> 
> soooo..... I tried to redirect again as:
> time dd if=/dev/hda of=/backup/system.img > /backup/system.msg >
> /backup/system.msg
> 
> and...  no go.  Any suggestions?

( time <cmd> ) 2>foo

This works because it's (a) redirecting the output of the
entire command "time <cmd>", not the output of "<cmd>"
alone, and (b) redirecting standard error, which is where "time"
writes the timing data. In general, the ( ) list notation
will glom all the output from the commands within ( ) into
a single pair of output and error streams.

So in your case,

( time dd if=/dev/hda of=/backup/system.img ) 2&>/backup/system.msg

should work.

Cheers,

-- Joe

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