topic Re: Scripting in Operating System - HP-UX

Scripting

Andrew Porter_1 — Thu, 10 Oct 2002 17:54:32 GMT

Can you assign stderr to a variable?

Re: Scripting

James R. Ferguson — Thu, 10 Oct 2002 18:03:32 GMT

Hi Andrew:

This works:

# X=`print -u2 "hello andrew" 2>&1`

Regards!

...JRF...

Re: Scripting

A. Clay Stephenson — Thu, 10 Oct 2002 18:05:34 GMT

You can do something like this:

XX=$(my_command 2>&1)

${XX} will then contain both stdout's and stderr's output but to get them separately is a bit more difficult.

ERRS=""
TFILE=/var/tmp/XX${$}.err

XX=$(my_command 2>${TFILE})
if [[ -s ${TFILE} ]]
then
ERRS=$(cat ${TFILE})
fi
rm -f ${TFILE}

Now ${XX} contains the output of stdout and ${ERRS} contains that of stderr

Re: Scripting

Andrew Porter_1 — Thu, 10 Oct 2002 18:08:40 GMT

Didn't work

Here what I am tring to do...

I am trying to put the elaspe time of a command into a variable

I was using

time {command}

to get the elaspe time

Re: Scripting

Jordan Bean — Thu, 10 Oct 2002 18:09:44 GMT

Do you mean that you want to capture stderr to a variable? Yes.

Using command substitution:

errormsg=$(command 2>&1 >/dev/ull)

The order of redirection is important! You first want to reassign stderr to what stdout is using, then redirect stdout to null if you don't it.

Using pipes and the shell's read command:

( command | read ouput ) 2>&1 | read error

This pipeline often confuses people. The grouping with parans is important because you want the stderr of the command to pass to the second read, not through first.

Re: Scripting

James R. Ferguson — Thu, 10 Oct 2002 18:13:31 GMT

Hi (again):

OK, thy this:

# time date 2> /tmp/mytime
# X=`# echo $X

Regards!

...JRF...

Re: Scripting

Darrell Allen — Thu, 10 Oct 2002 18:13:47 GMT

Yes you can.

V=$(ls junk 2>&1 >V.out)
In this case, $V contains stderr from "ls junk" and V.out contains stdout.

You could capture stderr and stdout both to the variable:
V=$(ls junk 2>&1)

Lastly, to capture stderr in a variable and send stdout to the screen:
V=$(ls junk 2>&1 >$(tty))

Darrell

Re: Scripting

Darrell Allen — Thu, 10 Oct 2002 18:25:16 GMT

Oops! I meant to say "If you want to send STDOUT to the bit bucket".

Darrell

Re: Scripting

Darrell Allen — Thu, 10 Oct 2002 18:25:25 GMT

For your example:

etime=(time {command} 2>&1 >$(tty))
echo $etime

If you want to send stderr to the bit bucket:
etime=(time {command} 2>&1 >/dev/null)

Darrell

Re: Scripting

Darrell Allen — Thu, 10 Oct 2002 18:29:14 GMT

That's weird! My "Oops" reply is posted before my "For your example" reply.

I'll have to point this out to Dan (the forums admin).

By the way, welcome to the forums Andrew. It's the best (even if there's been a few problems today with the site upgrade).

Darrell

Re: Scripting

Andrew Porter_1 — Thu, 10 Oct 2002 18:36:05 GMT

Thanks for all your help guys heres what I've come up with...

t=$(time {Command} 2>&1 >/dev/null|grep real|awk '{print $2}')

Thanks again

Re: Scripting

Jordan Bean — Thu, 10 Oct 2002 18:51:30 GMT

You can drop this grep this way:

t=$(time command 2>&1 >/dev/null | awk '$1~/^real$/{print $2}')

Or you can capture all times this to any array:

set -A t $(time command 2>&1 >/dev/null | awk '{print $2 $4 $6}')
echo real $t
echo all ${t[@]}
echo real ${t[0]} user ${t[1]} sys ${t[2]}

Re: Scripting

James R. Ferguson — Thu, 10 Oct 2002 18:56:52 GMT

Hi (again) Andrew:

Another way of capturing just the timing statistics was shown in my second post. All three metrics are assigned to the variable as a simple string.

Regards!

...JRF...