bash script to parse a specific record number and field from a text file?

Question

Assuming mpstat-log.txt file below, how can I parse the results of a file and get the %idle field for the first 4 CPUs 0-3. My guess is this is a job for grep, sed, cut, or awk but I am not experienced enough to know which is the best utility(s) to use for the job.

#!/bin/bash

for cpuIndex in {0..3}
do
   # Get percent idle from line of specified  cpuIndex
   cpuPercentIdle= # How to get a desired line and space separated field number?
   # Can you do math in a bash script ?
   cpuPercentUsed=$((100 - $cpuPercentId))
   echo "CPU $cpuIndex : Idle=$cpuPercentIdle, Used=$cpuPercentUsed"
   done
done

Script Output:

CPU 0 : Idle=45.18, Used=54.82
CPU 1 : Idle=96.33, Used=3.67
CPU 2 : Idle=95.65, Used=4.35
CPU 3 : Idle=72.09, Used=27.91

File:mpstat-log.txt

Average:     CPU   %user   %nice    %sys %iowait    %irq   %soft  %steal   %idle    intr/s
Average:     all   10.95    0.00    0.42    0.00    0.04    0.25    0.00   88.34   1586.71
Average:       0   51.50    0.00    3.32    0.00    0.00    0.00    0.00   45.18      0.00
Average:       1    3.67    0.00    0.00    0.00    0.00    0.00    0.00   96.33      2.66
Average:       2    4.35    0.00    0.00    0.00    0.00    0.00    0.00   95.65      0.00
Average:       3   27.57    0.00    0.33    0.00    0.00    0.00    0.00   72.09    997.34
Average:       4    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00     10.96
Average:       5    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00      0.00
Average:       6    0.00    0.00    0.00    0.00    0.00    0.00    0.00  100.00      0.00
Average:       7    0.00    0.00    0.00    0.00    0.00    1.67    0.00   98.33    575.75

Thanks in advance for any guidance and tips!

Costa · Accepted Answer · 2011-07-25 17:29:28Z

3

Just about all the tools you mention can do the job one way or another. Here's one with awk...

awk '{ if ( $2 <= 3 ) print $10; }' mpstat-log.txt

answered Jul 25, 2011 at 17:29

Costa

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1 Comment

glenn jackman Over a year ago

The more awk-ish way to write this is: awk '$2 <= 3 {print $10}'

Fredrik Pihl · Accepted Answer · 2011-07-25 17:41:50Z

2

Solution using awk:

{ if($2 ~ /[0-3]/) {
    print $10
  }
}

gives:

$ awk -f t.awk input
45.18
96.33
95.65
72.09

In pure bash, something like this perhaps:

#!/bin/bash

while read -a ARRAY
do
    if [[ "${ARRAY[1]}" =~ [0-3] ]]; then
        echo ${ARRAY[9]}
    fi
done < input

gives:

Bash cannot to floating point arithmetic, for that you can use bc. See this link for how you can use bc to do the math for you.

edited Jul 25, 2011 at 17:41

answered Jul 25, 2011 at 17:26

Fredrik Pihl

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3 Comments

glenn jackman Over a year ago

If there are > 10 CPUs, the regex /[0-3]/ will match too many

Fredrik Pihl Over a year ago

@glenn jackman - true, limit it to a single digit using /^[0-3]$/ instead.

Ed of the Mountain Over a year ago

Thank you all! The stuff that is possible to cobble together with grep, awk, sed, etc. makes my head spin. While very powerful, I feel sorry for the next Linux newbie that comes along to try and maintain. I guess I just need to leave descriptive comments.

Shawn Chin · Accepted Answer · 2011-07-26 09:16:40Z

1

$ awk '$2~/^[0-3]$/ {printf "CPU %d : Idle=%.2f, Used=%.2f\n",$2,$10,100-$10}' mpstat-log.txt
CPU 0 : Idle=45.18, Used=54.82
CPU 1 : Idle=96.33, Used=3.67
CPU 2 : Idle=95.65, Used=4.35
CPU 3 : Idle=72.09, Used=27.91

edited Jul 26, 2011 at 9:16

answered Jul 25, 2011 at 17:33

Shawn Chin

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2 Comments

glenn jackman Over a year ago

If there are > 10 CPUs, the regex /[0-3]/ will match too many

Shawn Chin Over a year ago

@glenn good point. Updated answer to cover more cases. Thanks

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