Bash: Adding the contents of a column to a variable

Question

So I have a file that contains some text, but there are some lines that contain only "Overall>5". (the number after > could be any number from 0 to 5).

The code I wrote:

let sumOfReviews=0

while read line; do awk -F ">" '{if($1=="Overall") ((sumOfReviews+=$2))}'; done<$file

echo $sumOfReviews

I tried splitting these lines into 2 columns at ">" and I want to add the number in the second column (5 in this case) to a variable. The problem is when I print out the value of the variable at the end it shows 0. Any thoughts? Thanks!

Andrey Tyukin · Accepted Answer · 2018-02-23 22:28:58Z

1

If called from the console, the following seems to do the job:

awk -F'>' '/Overall>[0-9]+/ { total += $2 } END { print total }' exampleData.txt

If you want to call it from inside bash, you have to enclose it in $( ... ):

#!/bin/bash

total="$(awk -F'>' '/Overall>[0-9]+/ { total += $2 } END { print total }' exampleData.txt)"

# do something with `total` here.

You cannot simply use awk as some sort of syntax inside bash, awk is a separate programming language, it is invoked as a completely separate process. You can try to build in some bash parameters into awks source code though.

answered Feb 23, 2018 at 22:28

Andrey Tyukin

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Comments

Ryan Henao · Accepted Answer · 2018-02-23 23:09:48Z

1

This can be done in a one line awk script.

awk 'BEGIN { FS=">"; sumOfReviews=0 } /^Overall>[0-5]/ { sumOfReviews+=$2 } END { print sumOfReviews }' < file

Explanation from Manpage:

An AWK program consists of a sequence of pattern-action statements and optional function definitions.

pattern   { action statements }

In this case we have used the BEGIN pattern to set the file separator to ">" and the sumOfReviews variable to 0.

We use the /^Overall>[0-5]/ regular expression pattern to match lines beginning with "Overall>" followed by a number 0-5 and if true add the $2 field to the sumOfReviews variable.

Finally we use the END pattern to output the final sumOfReviews value.

Example solution in a bash shell script:

#!/bin/bash

noAuthors=4 # set to 4 for example

sumOfReviews=$(awk 'BEGIN { FS=">"; sumOfReviews=0 } /^Overall>[0-5]/ 
{ sumOfReviews+=$2 } END { print sumOfReviews }' < file)

echo $(($sumOfReviews/$noAuthors))

edited Feb 23, 2018 at 23:09

answered Feb 23, 2018 at 22:34

Ryan Henao

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3 Comments

Lorena Mitoi Over a year ago

Hi there, thanks for your answer! From your code, it tells me that it doesn't recognize sumOfReviews as a command...

Ryan Henao Over a year ago

Interesting.. can you try making sure there's no spaces around the "=" sign, otherwise it's interpreted as a command eg. sumOfReviews=$(awk 'BEGIN ...

Lorena Mitoi Over a year ago

Nevermind, I was using spaces between the variable name and "=". It works now! Thanks!

chepner · Accepted Answer · 2018-02-23 22:28:41Z

0

awk and bash are two separate programs; they don't share variables. All you need is a single awk script:

awk -F '>' '$1 == "Overall" {reviews += $2}; END {print reviews}' "$file"

answered Feb 23, 2018 at 22:28

chepner

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2 Comments

Lorena Mitoi Over a year ago

Thanks, it seems to be working! Just a thought: I need to manipulate the value of "reviews" afterwards, can I use a pipe or something? I want to divide it by an already calculated number, stored in bash variable noAuthors. Sorry if it sounds so silly, I'm really at the beginning

Gordon Davisson Over a year ago

@LorenaMitoi awk can do the math itself, but you need to set an awk variable based on the value of that shell variable. Something like `awk -v noAuthors="$noAuthors" -F '>' '$1 == "Overall" {reviews += $2}; END {print reviews/noAuthors}' "$file"

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