Parsing multiline program output - bash

Question

I've recently been working on some lab assignments and in order to collect and analyze results well, I prepared a bash script to automate my job. It was my first attempt to create such script, thus it is not perfect and my question is strictly connected with improving it.
Exemplary output of the program is shown below, but I would like to make it more general for more purposes.
>>> VARIANT 1 <<<
Random number generator seed is 0xea3495cc76b34acc
Generate matrix 128 x 128 (16 KiB)
Performing 1024 random walks of 4096 steps.
> Total instructions: 170620482
> Instructions per cycle: 3.386
Time elapsed: 0.042127 seconds
Walks accrued elements worth: 534351478
All data I want to collect is always in different lines. My first attempt was running the same program twice (or more times depending on the amount of data) and then using grep in each run to extract the data I need by looking for the keyword. It is very inefficient, as there probably are some possibilities of parsing whole output of one run, but I could not come up with any idea. At the moment the script is:
#!/bin/bash
write() {
o1=$(./progname args | grep "Time" | grep -o -E '[0-9]+.[0-9]+')
o2=$(./progname args | grep "cycle" | grep -o -E '[0-9]+.[0-9]+')
o3=$(./progname args | grep "Total" | grep -o -E '[0-9]+.[0-9]+')
echo "$1 $o1 $o2 $o3"
}
for ((i = 1; i <= 10; i++)); do
write $i >> times.dat
done
It is worth mentioning that echoing results in one line is crucial, as I am using gnuplot later and having data in columns is perfect for that use. Sample output should be:
1 0.019306 3.369 170620476
2 0.019559 3.375 170620475
3 0.021971 3.334 170620478
4 0.020536 3.378 170620480
5 0.019692 3.390 170620475
6 0.020833 3.375 170620477
7 0.019951 3.450 170620477
8 0.019417 3.381 170620476
9 0.020105 3.374 170620476
10 0.020255 3.402 170620475
My question is: how could I improve the script to collect such data in just one program execution?

Answer 1

You could use awk here and could get values into an array and later access them by index 1,2 and 3 in case you want to do this in a single command.
myarr=($(your_program args | awk '/Total/{print $NF;next} /cycle/{print $NF;next} /Time/{print $(NF-1)}'))
OR use following to forcefully print all elements into a single line, which will not come in new lines if someone using " to keep new lines safe for values.
myarr=($(your_program args | awk '/Total/{val=$NF;next} /cycle/{val=(val?val OFS:"")$NF;next} /Time/{print val OFS $(NF-1)}'))
Explanation: Adding detailed explanation of awk program above.
awk ' ##Starting awk program from here.
/Total/{ ##Checking if a line has Total keyword in it then do following.
print $NF ##Printing last field of that line which has Total in it here.
next ##next keyword will skip all further statements from here.
}
/cycle/{ ##Checking if a line has cycle in it then do following.
print $NF ##Printing last field of that line which has cycle in it here.
next ##next keyword will skip all further statements from here.
}
/Time/{ ##Checking if a line has Time in it then do following.
print $(NF-1) ##Printing 2nd last field of that line which has Time in it here.
}'
To access individual items you could use like:
echo ${myarr[0]}, echo ${myarr[1]} and echo ${myarr[2]} for Total, cycle and time respectively.
Example to access all elements by loop in case you need:
for i in "${myarr[#]}"
do
echo $i
done

Answer 2

You can execute your program once and save the output at a variable.
o0=$(./progname args)
Then you can grep that saved string any times like this.
o1=$(echo "$o0" | grep "Time" | grep -o -E '[0-9]+.[0-9]+')

Answer 3

Assumptions:
each of the 3x search patterns (Time, cycle, Total) occur just once in a set of output from ./progname
format of ./progname output is always the same (ie, same number of space-separated items for each line of output)
I've created my own progname script that just does an echo of the sample output:
$ cat progname
echo ">>> VARIANT 1 <<<
Random number generator seed is 0xea3495cc76b34acc
Generate matrix 128 x 128 (16 KiB)
Performing 1024 random walks of 4096 steps.
> Total instructions: 170620482
> Instructions per cycle: 3.386
Time elapsed: 0.042127 seconds
Walks accrued elements worth: 534351478"
One awk solution to parse and print the desired values:
$ i=1
$ ./progname | awk -v i=${i} ' # assign awk variable "i" = ${i}
/Time/ { o1 = $3 } # o1 = field 3 of line that contains string "Time"
/cycle/ { o2 = $5 } # o2 = field 5 of line that contains string "cycle"
/Total/ { o3 = $4 } # o4 = field 4 of line that contains string "Total"
END { printf "%s %s %s %s\n", i, o1, o2, o3 } # print 4x variables to stdout
'
1 0.042127 3.386 170620482