How to write to an array the output of an awk command in UNIX?

Question

I have a flat file which contains the following

INDIA USA SA NZ AUS ARG GER BRA

so there are eight columns altogether . Now I want to store the indexes of those columns only which starts with A into an array. For that I tried the following statement

awk '{for(i=1;i<=NF;i++){if($i~/^A/){set -A newArray $i}}}' testUnix.txt

when I echo the file using

echo "${newArray[*]}"

it's printing 5 6 but whenever I am trying to get the length of that array

echo ${#newArray[@]}

its length is being shown as 1 only. Should not it be 2 ? I also tried

awk '{y = 0;for(i=1;i<=NF;i++){if($i~/^A/){newArray[y] = $i ; y++}}}' testUnix.txt

but also it's producing the same result. What am I missing ?Please explain. I intend to get the desired output 2.

The newArray in awk and bash are two different entities. So when you type echo "${newArray[*]}" its the value of bash array you are getting — nu11p01n73R
– nu11p01n73R, Commented Nov 18, 2014 at 13:57
Have to say - I think this is where things like Perl or Python start to come into their own. — Sobrique
– Sobrique, Commented Nov 18, 2014 at 14:06

fedorqui · Accepted Answer · 2014-11-18 14:18:53Z

1

No need for awk. You can loop through the elements and check if they start with A:

r="INDIA USA SA NZ AUS ARG GER BRA"
arr=()
for w in $r
do
    [[ $w == A* ]] && arr+=("$w")
done

If you execute it then the arr array contains:

$ for i in  "${arr[@]}"; do echo "$i"; done
AUS
ARG

And to confirm that is has two elements, let's count them:

$ echo "${#arr[@]}"
2

What is happening with your aproach?

awk '{for(i=1;i<=NF;i++){if($i~/^A/){set -A newArray $i}}}' testUnix.txt

this says set -A newArray but it is not really defining the variable in bash, because you are in awk.

edited Nov 18, 2014 at 14:18

answered Nov 18, 2014 at 14:00

fedorqui

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Comments

Gilles Quénot · Accepted Answer · 2014-11-18 14:00:12Z

1

What I would do to have a bash array :

bash_arr=( $(awk '{for(i=1;i<=NF;i++){if($i~/^A/){print $i}}}' file) )
echo "${bash_arr[@]}"
AUS ARG

And you don't even need awk in reality, bash is capable of doing regex :

for word in $(<file); do [[ $word =~ ^A ]] && basharr+=( "$word" ); done

answered Nov 18, 2014 at 14:00

Gilles Quénot

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2 Comments

StrugglingCoder Over a year ago

it's length is still 1 :(

Gilles Quénot Over a year ago

??? What's the problem ? You have the 2 searched elements. Dunno what's wrong. The index start @ zero !

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