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I have the following bash script which works fine until I get to number 9 (/dev/sdj) where it does not produce the expected output.

hdd1="$(sudo fdisk -l | grep "Disk /dev/sd" | awk '{print$2}' | sed 's/://g')"
counter=0
function check {
    i="0"
    while [ $i == "0" ]
    do
        hdd2="$(sudo fdisk -l | grep "Disk /dev/sd" | awk '{print$2}' | sed 's/://g')"
        hdd1_count=$(echo "$hdd1" | wc -l)
        hdd2_count=$(echo "$hdd2" | wc -l)
        # Check if added or removed
        if [[ "$hdd1_count" < "$hdd2_count" ]]
        then
            echo -e "\e[32mHDD ADDED\e[0m"
            counter=$((counter+1))
            echo "Total HDD: $counter"
            echo "HDD1: $hdd1"
            echo "HDD2: $hdd2"
            hdd1=$hdd2
            echo "HDD1 is now: $hdd1"
            # Get last disk in var
            last=$(echo "${hdd1##*$'\n'}")
            echo "LAST: $last"
        elif [[ "$hdd1_count" > "$hdd2_count" ]]
        then
        echo -e "\e[32mHDD REMOVED\e[0m"
            counter=$((counter-1))
            echo "Total HDD: $counter"
            echo "HDD1: $hdd1"
            echo "HDD2: $hdd2"
            hdd1=$hdd2
            echo "HDD1 is now: $hdd1"
            # Get last disk in var
            last=$(echo "${hdd1##*$'\n'}")
            echo "LAST: $last"
        fi
    done
}

check

Here is the output:

HDD ADDED
Total HDD: 1
HDD1: /dev/sda
HDD2: /dev/sda
/dev/sdb
HDD1 is now: /dev/sda
/dev/sdb
LAST: /dev/sdb

This works until /dev/sdi as followed:

HDD ADDED
Total HDD: 8
HDD1: /dev/sda
/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
/dev/sdf
/dev/sdg
/dev/sdh
HDD2: /dev/sda
/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
/dev/sdf
/dev/sdg
/dev/sdh
/dev/sdi
HDD1 is now: /dev/sda
/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
/dev/sdf
/dev/sdg
/dev/sdh
/dev/sdi
LAST: /dev/sdi

Then I get to insert disk 9 and the output changes but I cannot find the problem why it isn't going on like expected. Here is the output:

HDD REMOVED
Total HDD: 7
HDD1: /dev/sda
/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
/dev/sdf
/dev/sdg
/dev/sdh
/dev/sdi
HDD2: /dev/sda
/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
/dev/sdf
/dev/sdg
/dev/sdh
/dev/sdi
/dev/sdj
HDD1 is now: /dev/sda
/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
/dev/sdf
/dev/sdg
/dev/sdh
/dev/sdi
/dev/sdj
LAST: /dev/sdj

I have changed the script now for 2 days in a row but I keep getting the same result. Can someone spot the problem?

EDIT:

-lt and -gt did the trick, thanks!

Improve this question
4
  • 1
    This might help: How to debug a bash script? Commented Jun 19, 2019 at 9:15
  • 1
    To strip useless code paste your script there: shellcheck.net Commented Jun 19, 2019 at 9:17
  • 2
    It probably has to do with < being lexicographic comparison, not arithmetic comparison. 10 < 9 because 1 < 9. You're probably looking for -lt. Also, consider using arrays instead of whatever it is you're doing now. Commented Jun 19, 2019 at 9:19
  • 2
    Also as a hint: instead of awking / seding fdisk output, you can simply iterate through /dev/sd[a-z] (e.g. for disk in /dev/sd[a-z]; do .. done). Commented Jun 19, 2019 at 9:49

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