How to use two arrays in a shell script for loop?

Question

I have two arrays in a bash script, every array have same number of elements, I need to write 2nd array's every element for every element in the first array in a for loop

first array name: ARR_MPOINT

second array name: ARR_LVNAME

piece of the script:

ARR_MPOINT=(/tmp /var /log);
ARR_LVNAME=(lv_tmp lv_var lv_log)

for MPOINT in "${ARR_MPOINT[@]}"
    do
        echo "/dev/mapper/VolGroup01-${ARR_LVNAME[@]}     $MPOINT         xfs      defaults        1 2" 
    done

I need to print below output

/dev/mapper/VolGroup01-lv_tmp      /tmp        xfs      defaults        1 2
/dev/mapper/VolGroup01-lv_var      /var        xfs      defaults        1 2
/dev/mapper/VolGroup01-lv_log      /log        xfs      defaults        1 2

A nested for loop that iterates over `ARR_LVNAME` should do the trick. Just realized you want 3 iterations instead of 9 but access both arrays at the same index. — Jonny Henly, Jun 29 '17 at 05:32
Use a for loop like `for i in {0..$ARRAY_SIZE}`. Then something like `echo "/dev/mapper/VolGroup01-${ARR_LVNAME[i]} ${ARR_MPOINT[i]} ..."` — Jonny Henly, Jun 29 '17 at 05:39
Have a look at this answer: https://stackoverflow.com/questions/17403498/iterate-over-two-arrays-simultaneously-in-bash — m13r, Jun 29 '17 at 05:43

score 1 · Answer 1 · answered Jun 29 '17 at 05:45

1

If the arrays have the same length you can access the elements by index:

for ((i=0; i<${#ARR_MPOINT[@]}; i++)); do
    echo "/dev/mapper/VolGroup01-${ARR_LVNAME[i]}     ${ARR_MPOINT[i]}         xfs      defaults        1 2" 
done

answered Jun 29 '17 at 05:45

mata

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thanks this will work. I will try this. – Ramana Jun 29 '17 at 05:54

score 0 · Answer 2 · answered Jun 29 '17 at 05:40

0

You could replace / with lv_ and only use the first array to get the output:

for MPOINT in "${ARR_MPOINT[@]}"; do
    echo "/dev/mapper/VolGroup01-${MPOINT//\//lv_} $MPOINT xfs defaults 1 2" 
done

answered Jun 29 '17 at 05:40

m13r

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How to use two arrays in a shell script for loop?

2 Answers2