在bash shell脚本中检查数组索引

Question

I'm new to shell scripting...can anyone tell me how I can check whether I am on the first element of the array in my very first 'if' statement? It seems to be making i into something other than an integer.

#! /bin/bash

namelist=($(lsblk -d -n -o NAME))
sizelist=($(lsblk -d -n -o SIZE))
seriallist=($(lsblk -d -n -o SERIAL))

IFS=$'\n'
modellist=($(lsblk -d -n -o MODEL))

echo "*********** HARD DRIVE DATA SCRIPT ***********"
echo "This script lets you choose the hard drives"
echo " "
echo "********************************************"
echo "* Step one: Choose your hard drive         *"
echo "********************************************"

for i in "${namelist[@]}"
do
    if [ "$i" -eq "0" ]
    then
        echo "First hard drive:"
    else
        echo "Next hard drive:"
    fi
    echo "* Size: ${sizelist[$i]}B"
    echo "* Model: ${modellist[$i]}"
    echo "* Serial number: ${seriallist[$i]}"
    echo "* Linux device name: ${namelist[$i]}"
    echo "* Partition List:"
    echo "Number  Name  Formatted as"
    lsblk -n -o NAME,LABEL,FSTYPE /dev/${namelist[$i]} | tail -n +2
    ((i++))
done

Answer 1

i=0
for item in "${namelist[@]}"
do
    echo $item # so you can see what your assumption actually is
    if [ "$i" -eq "0" ]
    then
        echo "First hard drive:"
    else
        echo "Next hard drive:"
    fi
    echo "* Size: ${sizelist[$i]}B"
    echo "* Model: ${modellist[$i]}"
    echo "* Serial number: ${seriallist[$i]}"
    echo "* Linux device name: ${namelist[$i]}"
    echo "* Partition List:"
    echo "Number  Name  Formatted as"
    lsblk -n -o NAME,LABEL,FSTYPE /dev/${namelist[$i]} | tail -n +2
    ((i++))
done

You're mixing up for syntaxes. item refers here to each element of the array, not i the counter. Note that it won't work unless you get serials for each device that you end up with, which you probably won't. In other words, you are assuming the counts of each array you generated is the same, that's not necessarily the case here. I get 0 results for serial in my system, for example, whether as root or as normal user. The only way I know to get serials is far more complex than you have here, so I won't attempt describe it, and it also won't always return values for your serials for each device.

Also note that you will get results for fdx and srx with this logic, that is, floppy drives and optical drives, which you probably don't want.

I also tested, and get nothing for LABEL FSTYPE either, by the way. So this method wouldn't work on a Debian type system, I can't speak for others.

If you were to use:

for i in "${!namelist[@]}"

then you would not use ((i++)), which is only required if nothing else is changing i.

This would work better using awk, which is designed to create such reports, but that's outside the scope of your question.