Why the output of iostat is not redirected to the file in the following command:
iostat -x 3 | awk '/sda/ { print $11, $12}' > /tmp/disk_utilization
Is iostat behaving differently than any other command?
Thx in advance
Looks like you need to add a count to tell the stream when to terminate( man iostat ). You're only adding the interval:
If the interval parameter is specified without the count parameter, the iostat command generates reports continuously.
When I try:
iostat -x 3 6 | awk '/sda/ { print $11, $12}' > outfile
the 6 tells iostat to stop after 6 iterations of 3 second intervals. After the iterations iostat completes and I get an output file.
Alternatively, you could pick some expression to cause the awk script to exit. When I try:
iostat -x 3 | awk -v max=10 '/sda/ { print $11, $12; max++ } NR > max { exit } ' > outfile2
I get just 3 lines in output2 which makes sense because iostat -x produces about a screens worth of lines of output to the screen.
You could also force the awk to fflush(stdout) in each print cycle:
iostat -x 3 | awk '/sda/ { print $11, $12; fflush(stdout) }' > output3
and then close iostat with a <ctrl+c> from the shell.