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redirection of stdout & stderr

Posted on 2001-08-08
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Last Modified: 2012-06-27
I've been trying to redirect output of errors from a script job (through cron) to mailx. This works fine, but I loose the stderr going out to the logfile. Ideally I'd like to get stderr & stdout to a log file AND stderr on it's own to mailx.
e.g.
/tmp/test > /tmp/test.log 2 > 'mailx root'

I've been playing with variations of using "tee" to output to two destinations, but no joy...
I've also tried to manipulate file descriptors but still no joy...
e.g.
/tmp/test > /tmp/test.log 3>&2 2>&1 3 > 'mailx root'

am I going in the right direction or lost altogether ?
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Question by:ferguswilson
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by:ecw
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/tmp/test 2>&1 >/tmp/test.log | mailx root
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by:ferguswilson
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ecw,
your suggestion is doing the same thing
it just directs the errors FROM the logfile TO mailx
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by:ecw
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If you don't mind using a tempfile, maybe ...

  (/tmp/test 2>&1 1>&3 | tee /tmp/test.err) > /tmp/test.log 3>&1 ; test -z /tmp/test.err || mailx root < /tmp/test.err

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by:ferguswilson
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not really, temp files wouldn't really be a good idea. If I was to go down the road of extra files, I'd be taking a different route than this.
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ahoffmann earned 100 total points
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(script > logfile) 2>&1|tee -a logfile|mailx root
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by:paulqna
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Basically you can:

  1.redirect stdout to a file
  2.redirect stderr to a file
  3.redirect stdout to a stderr
  4.redirect stderr to a stdout
  5.redirect stderr and stdout to a file
  6.redirect stderr and stdout to stdout
  7.redirect stderr and stdout to stderr

Consider this:
exec 3>&1; script 2>&1 1>&3 3>&- | mailx root 1>&2 3>&-

Normal output would be unaffected. The closes there were in case something really cared about all its FDs. We send stderr to sed, and then put it back out 2.

Or did I misunderstood the original question ? ;)
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by:ferguswilson
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ahoffmann,
this done the trick for me, thanks.
for the record though, it sent an email even if there wern't any errors going to stderr;
e.g.
Your "cron" job
(/sys/test > /sys/test.log) 2>&1|tee /sys/test.log|mailx root
 produced the following output:
UX:mailx: WARNING: No message !?!  Message not sent

...but putting in || at the end resolved it
(/sys/test > /sys/test.log) 2>&1|tee /sys/test.log||mailx root

thanks for your help,
Fergus.
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by:ahoffmann
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aah, nice trick: ||
You got used to shells ;-)
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