Grep specific paragraph of command output in Linux

Question

I'm trying to parse iostat -x 1 2 command's output to monitor remote computer from my java application.

This is the output:

Linux 2.6.39-400.126.1.el5uek (abcprod.abc-en.local)         02/27/2014

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           2.57    0.00    0.87    0.01    0.00   96.56

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00    54.24  0.35 10.64     6.95   518.97    47.89     0.01    1.06   0.19   0.21
sda1              0.00     0.00  0.00  0.00     0.00     0.00    68.40     0.00    2.08   0.94   0.00
sda2              0.00    54.23  0.35 10.64     6.94   518.97    47.89     0.01    1.06   0.19   0.21
dm-0              0.00     0.00  0.18 48.77     4.18   390.19     8.06     0.08    1.63   0.02   0.10
dm-1              0.00     0.00  0.00  0.00     0.00     0.00     8.00     0.00    1.06   0.18   0.00
dm-2              0.00     0.00  0.00  0.00     0.00     0.00     8.00     0.00    1.78   0.14   0.00
dm-3              0.00     0.00  0.17 16.10     2.76   128.78     8.09     0.03    2.10   0.07   0.11

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          11.61    0.00    3.20    0.00    0.00   85.19

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00   191.00  0.00 43.00     0.00  1872.00    43.53     0.00    0.09   0.05   0.20
sda1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda2              0.00   191.00  0.00 43.00     0.00  1872.00    43.53     0.00    0.09   0.05   0.20
dm-0              0.00     0.00  0.00 234.00     0.00  1872.00     8.00     0.00    0.02   0.01   0.20
dm-1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-2              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00

I only need the second part of the output(beginning from fourth paragraph):

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
          11.61    0.00    3.20    0.00    0.00   85.19

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00   191.00  0.00 43.00     0.00  1872.00    43.53     0.00    0.09   0.05   0.20
sda1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
sda2              0.00   191.00  0.00 43.00     0.00  1872.00    43.53     0.00    0.09   0.05   0.20
dm-0              0.00     0.00  0.00 234.00     0.00  1872.00     8.00     0.00    0.02   0.01   0.20
dm-1              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-2              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00
dm-3              0.00     0.00  0.00  0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Do not how to use grep to do it, but you can use perl:

iostat -x 1 2 | perl -e 'local $/=""; @p=<STDIN>; print @p[3,4];'

Some explanations:

local, see perlsub

A local modifies its listed variables to be "local" to the enclosing block, eval, or do FILE --and to any subroutine called from within that block. A local just gives temporary values to global (meaning package) variables.
$/, see perlvar

The input record separator, newline by default. This influences Perl's idea of what a "line" is.

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Feb 27, 2014 at 8:49

Lee Duhem

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1 Comment

AloneInTheDark Over a year ago

That solves the problem. What does this "local" parameter do?

deimus · Accepted Answer · 2014-02-27 08:44:47Z

1

If the number of the lines for the first paragraph is fixed you can use sed like this

iostat -x 1 2 | sed 'N,$!d' - where N is the number of the lines of first paragraph

answered Feb 27, 2014 at 8:44

deimus

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2 Comments

AloneInTheDark Over a year ago

+1 for temporary solution. But when there is more devices, this code won't work right?

deimus Over a year ago

Yes, somehow you have to figure out the number of the devices first

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