Arithmetic calculation in shell scripting-bash - bash

Question

I have an input notepad file as shown below:
sample input file:
vegetables and rates
kg rate total
Tomato 4 50 100
potato 2 60 120
Beans 3 80 240
Overalltotal: (100+120++240) = 460
I need to multiply the column 2 and column 3 and check the total if it is right and the overall total as well. If that's not right we need to print in the same file as an error message as shown below
enter code here
sample output file:
vegetables and rates
kg rate vegtotal
Tomato 4 50 200
potato 2 60 120
Beans 3 80 240
Overalltotal: (200+120++240) = 560
Error in calculations:
Vegtotal for tomato is wrong: It should be 200 instead of 100
Overalltotal is wrong: It should be 560 instead of 460
Code so far:
for f in Date*.log; do
awk 'NR>1{ a[$1]=$2*$3 }{ print }END{ printf("\n");
for(i in a)
{ if(a[i]!=$4)
{ print i,"Error in calculations",a[i] }
} }' "$f" > tmpfile && mv tmpfile "$f";
done
It calculates the total but not comparing the values. How can I compare them and print to same file?

Answer 1

Complex awk solution:
awk 'NF && NR>1 && $0!~/total:/{
r=$2*$3; v=(v!="")? v"+"r : r;
if(r!=$4){ veg_er[$1]=r" instead of "$4 }
err_t+=$4; t+=r; $4=r
}
$0~/total/ && err_t {
print $1,"("v")",$3,t; print "Error in calculations:";
for(i in veg_er) { print "Veg total for "i" is wrong: it should be "veg_er[i] }
print "Overalltotal is wrong: It should be "t" instead of "err_t; next
}1' inputfile
The output:
kg rate total
Tomato 4 50 200
potato 2 60 120
Beans 3 80 240
Overalltotal: (200+120+240) = 560
Error in calculations:
Veg total for Tomato is wrong: it should be 200 instead of 100
Overalltotal is wrong: It should be 560 instead of 460
Details:
NF && NR>1 && $0!~/total:/ - considering veg lines (excuding header and total lines)
r=$2*$3 - the result of product of the 2nd and 3rd fields
v=(v!="")? v"+"r : r - concatenating resulting product values
veg_er - the array containing erroneous vegs info (veg name, erroneous product value, and real product value)
err_t+=$4 - accumulating erroneous total value
t+=r - accumulating real total value
$0~/total/ && err_t - processing total line and error events

Answer 2

Input
akshay#db-3325:/tmp$ cat file
kg rate total
Tomato 4 50 100
potato 2 60 120
Beans 3 80 240
Output
akshay#db-3325:/tmp$ awk 'FNR>1{sum+= $2 * $3 }1;END{print "Total : "sum}' file
kg rate total
Tomato 4 50 100
potato 2 60 120
Beans 3 80 240
Total : 560
Explanation
awk ' # call awk
FNR>1{ # if no of lines of current file is greater than 1,
# then , this is to skip first row
sum+= $2 * $3 # sum total which is product of value
# in column2 and column3
}1; # 1 at the end does default operation,
# that is print current record ( print $0 )
# if you want to skip record being printed remove "1", so that script just prints total
END{ # end block
print "Total : "sum # print sum
}
' file