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Editorial Team
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Asked: 2026-06-11T14:25:31+00:00

The so-far expertly crafted script iostat -p -x 1 2| grep $1[^[:digit:]] | awk

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The so-far expertly crafted script 

iostat -p -x 1 2| grep $1[^[:digit:]] | awk '{print $9}'

will return two lines:

0.16
0.00

because iostat is taking two samples. But you already knew that. My question is since you and I both know it will be exactly two lines every time, how I pick out exactly the second?

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1 Answer

  1. Editorial Team

    Add NR==2 before {print $9} to tell awk to match record 2.

    For example, on my system,

    $ iostat -x /dev/sda 1 2 | grep sda

$ iostat -x /dev/sda 1 2 | grep sda | awk 'NR==1 {print $9}'

$ iostat -x /dev/sda 1 2 | grep sda | awk 'NR==2 {print $9}'

    produced

    sda               0.11     1.04    2.00    1.28   125.95    63.24   115.15     0.07   21.04    4.66   46.60   2.36   0.78
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
0.07
0.00

    where that “0.00” line is the result of the third command.

    Additional note: It isn’t necessary to run a separate grep command, as awk can match text. However, the awk script then needs an index variable. The first of the following examples is a simple grep to show what awk works on. The next two examples are straightforward awk code that has a match test to increment an index and another match test plus index test to print. The last example shows how to get rid of extra appearances of the match expression. Note, in these examples I replaced print $9 with print for clarity, and $1[^[:digit:]] with sda[^0-9]. Here are the examples which do the matching in awk instead of in grep:

    $ iostat -p -x 1 2  | grep 'sda '
sda               0.11     1.04    2.00    1.28   125.70    63.16   115.09     0.07   21.04    4.66   46.57   2.36   0.78
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

$ iostat -p -x 1 2  | awk '/sda[^0-9]/ {++t} t==1 && /sda[^0-9]/ {print}'
sda               0.11     1.04    2.00    1.28   125.70    63.16   115.09     0.07   21.04    4.66   46.57   2.36   0.78

$ iostat -p -x 1 2  | awk '/sda[^0-9]/ {++t} t==2 && /sda[^0-9]/ {print}'
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00

$ iostat -p -x 1 4  | awk '/sda[^0-9]/ && t++ && t==2 {print}'
sda               0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00    0.00    0.00   0.00   0.00
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