shell: write integer division result to a variable and print floating number

Question

I'm trying to write a shell script and plan to calculate a simple division using two variables inside the script. I couldn't get it to work. It's some kind of syntax error.

Here is part of my code, named test.sh

    awk '{a+=$5} END {print a}' $variable1 > casenum
    awk '{a+=$5} END {print a}' $variable2 > controlnum
    score=$(echo "scale=4; $casenum/$controlnum" | bc)
    printf "%s\t%s\t%.4f\n", $variable3 $variable4 $score

It's just the $score that doesn't work.

I tried to use either

sh test.sh

or

bash test.sh

but neither worked. The error message is:

(standard_in) 1: syntax error

Does anyone know how to make it work? Thanks so much!

Do you intend for awk to read from a file named in the variable $variable1? And do you really want the output of that awk script to go to a file named casenum which happens to be the name of a variable that you use in the echo? I suspect your problems are primarily the result of confusion about basic shell syntax. — William Pursell
– William Pursell, Commented Oct 29, 2013 at 14:31
exactly, fedorqui's answer mentioned the same thing. thanks! — olala
– olala, Commented Oct 29, 2013 at 15:35

fedorqui · Accepted Answer · 2013-10-29 14:31:10Z

2

You are outputting to files, not to vars. For this, you need var=$(command). Hence, this should make it:

casenum=$(awk '{a+=$5} END {print a}' $variable1)
controlnum=$(awk '{a+=$5} END {print a}' $variable2)
score=$(echo "scale=4; $casenum/$controlnum" | bc)
printf "%s\t%s\t%.4f\n", $variable3 $variable4 $score

Note $variable1 and $variable2 should be file names. Otherwise, indicate it.

answered Oct 29, 2013 at 14:31

fedorqui

293k113 gold badges592 silver badges640 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

olala Over a year ago

$variable1 and $variable2 are variables in my script. They were working fine. What would you do to indicate it?

olala Over a year ago

i see. For simplicity I didn't include the previous lines. They are used as variable. I just accepted it!

fedorqui Over a year ago

Great, now I understand, @user2157668 :)

ShinTakezou · Accepted Answer · 2013-10-29 14:44:15Z

First your $variable1 and $variable2 must expand to a name of an existing file; but that's not a syntax error, it's just a fact that makes your code wrong, unless you mean really to cope with files containing numbers and accumulating the sum of the fifth field into a file. Since casenum and controlnum are not assigned (in fact you write the awk result to a file, not into a variable), your score computation expands to

score=$(echo "scale=4; /" | bc)

which is wrong (Syntax error comes from this).

Then, the same problem with $variable3 and $variable4. Are they holding a value? Have you assigned them with something like

  variable=...

? Otherwise they will expand as "". Fixing these (including assigning casenum and controlnum), will fix everything, since basically the only syntax error is when bc tries to interpret the command / without operands. (And the comma after the printf is not needed).

The way you assign the output of execution of a command to a variable is

  var=$(command)

or

  var=`command`

jkshah · Accepted Answer · 2013-10-29 14:51:27Z

1

If I understand your commands properly, you could combine calculation of score with a single awk statement as follows

score=$(awk 'NR==FNR {a+=$5; next} {b+=$5} END {printf "%.4f", a/b}' $variable1 $variable2)

This is with assumption that $variable1 and $variable2 are valid file names

Refer to @fedorqui's solution if you want to stick to your approach of 2 awk and 1 bc.

edited Oct 29, 2013 at 14:51

answered Oct 29, 2013 at 14:46

jkshah

11.8k6 gold badges37 silver badges46 bronze badges

Collectives™ on Stack Overflow

shell: write integer division result to a variable and print floating number

3 Answers 3

3 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related