add two variables in bash

Question

I have a fileA that contains:

  0012,001650,0089

I want to get the sum of column 1 and column 2 and the quotient of column 3 and 60. Using awk I tried this

  col1=`awk -F, '{print $1}' $fileA | sed 's/0*//'`
  col2=`awk -F, '{print $2}' $fileA | sed 's/0*//'`
  col3=`awk -F, '{print $3}' $fileA | sed 's/0*//'`

  sum=$((col1 + col2))
  qou=$((col3 / 60))

But I got this error:

apn_processing.sh[226]: col1 + col2: The specified number is not valid for this command.

Can you give me another solution for this?

Do not use old and deprecated back-tics, use parentheses like this: col1=$(awk -F, '{print $1}' $fileA | sed 's/0*//') — Jotne
– Jotne, Commented Mar 3, 2015 at 7:06

Ed Morton · Accepted Answer · 2015-03-03 00:14:59Z

3

shell is for sequencing calls to tools, that's all. If you're just doing text processing then do the whole job in awk:

$ awk -F, '{
  sum = $1 + $2
  quo = $3 / 60
  print sum, quo
}' "$fileA"
1662 1.48333

answered Mar 3, 2015 at 0:14

Ed Morton

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2 Comments

starpark Over a year ago

how about if i only need whole number (rounded off) for the output?

mklement0 Over a year ago

@newbie: Then you can use awk's printf function with the appropriate format; printf "%d %d\n", sum, quo will truncate the fractional part.

glenn jackman · Accepted Answer · 2015-03-03 00:15:29Z

3

You don't need to call awk 3 times to extract the fields:

$ IFS=, read -r a b c < file
$ echo $a
0012
$ echo $b
001650
$ echo $c
0089
$ echo $((10#$a + 10#$b))
1662
$ echo $((10#$c / 60))
1
$ bc  <<< "scale=3; $c/60"
1.483

In bash math, you can specific a number's base with the notation base#number, so you don't get tripped up by invalid octal numbers like "0089"

answered Mar 3, 2015 at 0:15

glenn jackman

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Comments

Tom Fenech · Accepted Answer · 2015-03-03 00:06:55Z

1

Especially since you're dealing with floating point arithmetic, I would recommend performing the calculations in awk:

sum=$(awk -F, '{print $1+$2}' file)
qou=$(awk -F, '{print $3/60}' file)

answered Mar 3, 2015 at 0:06

Tom Fenech

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Comments

John1024 · Accepted Answer · 2015-03-03 07:11:32Z

1

Assuming that you have reason to want to get the answers into shell variables:

$ read sum quo < <(awk -F, '{print ($1+$2), $3/60}' "$fileA")
$ echo $sum $quo
1662 1.48333

Unlike bash, awk has no problem with leading zeros on numbers that it receives as input. For example, observe that the following works just fine:

$ echo 016 08 | awk '{print $1, $2, $1+$2, $1/$2}'
016 08 24 2

Aside

mklement0 points out in the comments that GNU awk will try to interpret numbers beginning with zero as octal, falling back to decimal, if they are program constants as opposed to input. Consider:

$ awk 'BEGIN{a=016;b=08; print a, b, a+b, a/b}'
14 8 22 1.75

In the above, 016 is treated as octal. By contrast, 08, which is not a legal octal number, is treated as decimal.

edited Mar 3, 2015 at 7:11

answered Mar 3, 2015 at 0:08

John1024

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2 Comments

mklement0 Over a year ago

Nicely done; as an aside: GNU awk somewhat ambiguously does recognize octals as literals inside a script (not through input), and falls back to decimal interpretation; try gawk 'BEGIN {print 010}' vs. gawk 'BEGIN {print 08}'.

John1024 Over a year ago

@mklement0 Interesting! I added that to the answer.

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