[SOLVED] Modify a column with awk and a bash script

Modify a column with awk and a bash script

I have a test.txt file looking like this :

a,1,A
b,2,B
c,3,C
d,4,D
e,5,E
f,6,F

I want to modify the second field with some condition :

if value is 1 I modify it to 1_PLUS

if value is 4 I modify it to 4_PLUS

if value is 6 I modify it to 6_PLUS

otherwise modify it to an empty field.

The final file will look like this :

a,1_PLUS,A
b,,B
c,,C
d,4_PLUS,D
e,5,E
f,6_PLUS,F

I wrote a bash script test.sh to do the substitution :

ITEM=$1
case $ITEM in
  1)
    LOC=1_PLUS
    ;;
  4)
    LOC=4_PLUS
    ;;
  6)
    LOC=6_PLUS
    ;;
  *)
    LOC=
    ;;
esac
echo $LOC

Then I launch the command like this : I give the $2 argument to my test.sh script to do the substitution and modify the $2 in awk with this new value.

cat test.txt | awk -F, '{$2=$(system("bash ./test.sh "$2))}'

The result is :

1_PLUS


4_PLUS 
 
6_PLUS

So I think I'm close to the solution but I don't understand why modifying the second field with $2=(result of my bash script) doesn't work

I need to keep the cat test.txt | first because in real life I have a longer command...

Thanx for your help

Solution

To "modify a column with awk and a bash script":

awk 'BEGIN{FS=OFS=","} {cmd="bash ./test.sh " $2; cmd | getline $2; close(cmd); print}' test.txt

Output:

a,1_PLUS,A
b,,B
c,,C
d,4_PLUS,D
e,,E
f,6_PLUS,F

If you use system() its output is printed automatically. That's not what you want here.