On 1/15/2013 9:30 PM, Greg Larkin wrote:
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On 1/15/13 12:42 PM, Nikos Vassiliadis wrote:
Hi,
A bit of an OT question. I am writing a bourne shell script that
collects data from a router. Since netstat & vmstat can run for a
numbers of iterations I thought I would use just that:
stats() ( nstats=`netstat -I ng0 -q 1 60 | tail -1` &
rawdata=`vmstat -c 2 60 | tail -1` wait ...
The logic was: 1. run the first process in the bg 2. run the second
process 3. wait to make sure the first process has finished 4.
continue further
It makes perfect sense why this doesn't work. Both commands run in
the foreground.
I am going to split the time between netstat and vmstat. So, it
will be 30 seconds of netstat and 30 seconds of vmstat.
But I am still interested/curious how one should go for this using
the shell. So, can this be done without files? Any thoughts?
Thanks, Nikos
Hi Nikos,
As far as I can tell, the backticks are what's causing the problem.
Even though you put the first command in the background (maybe with
the & inside the backticks, though), the assignment to the nstats
variables causes the script to block.
If you switch to using temp files, you may have more luck, e.g.:
netstat -w 1 -I ng0 -q 60 | tail -1 > /tmp/netstat.$$ &
npid=`echo $!`
vmstat -w 2 -c 60 | tail -1 > /tmp/vmstat.$$ &
vpid=`echo $!`
wait $npid
nstats=`cat /tmp/netstat.$$`
rm -f /tmp/netstat.$$
wait $vpid
rawdata=`cat /tmp/vmstat.$$`
rm -f /tmp/vmstat.$$`
Yes, this looks probably like something I will use too.
Just for the fun of it and using a separator(Robert's idea), I came up
with this:
delay=10
a=$(
(
echo netstat `netstat -I ng0 -q 1 $delay | tail -1` netstat
) &
(
echo vmstat `vmstat -c 2 $delay | tail -1` vmstat
)
)
echo $a
If someone else has something else to add I'll be glad to hear it,
no matter how crazy!
Thanks for your answers Greg & Robert,
Nikos
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