I am writing a script that's picking up two values from a file and then subtracting them.But I am unable to do substraction as it is throwing error.
res1= awk 'FNR == '${num1}' {print $1}' /home/shell/test.txt
res2= awk 'FNR == '${num2}' {print $1}' /home/shell/test.txt
res= $((res2 - res1))
echo $res
I also tried expr = `expr $res2 -$res1` but it didn't work. please help me so as to get the desired result.
your assignments for res1/res2 are wrong. It should be
res1=$(awk 'FNR == '${num1}' {print $1}' /home/shell/test.txt)
However, you can do it all in awk
$ num1=5; num2=2; awk -v n1=${num1} -v n2=${num2} 'FNR==n1{r1=$1;f1=1}
FNR==n2{r2=$1;f2=1}
f1&&f2{print r1-r2; exit}' <(seq 5)
3
This is because there is one space char after each = sign: res1= awk
Remove the spaces and use $( command ) to execute a command and gather its output.
Give a try to this:
res1="$(awk -v num=${num1} 'FNR == num {print $1}' /home/shell/test.txt)"
res2="$(awk -v num=${num2} 'FNR == num {print $1}' /home/shell/test.txt)"
res=$(( res2 - res1 ))
printf "%d\n" ${res}
I had read in another answer that it is preferred to pass variable's value to awk script using -v var_name=value, rather than concatenating strings.
