How to swap array element in bash shell linux? - arrays

Question

I have a problem regarding about the syntax on how to swap the element value in an array.
array="5 3 2 1 4"
echo "${array[*]}"
changed=1
while [ $changed != 0 ]
do
changed=0
for (( i=0 ; i<=${#array[#]}-1 ; i++ ))
do
if [ ${array[$i]} -gt ${array[$i+1]} ]
then
tmp=${array[$i]}
array[$i]=${array[$i+1]}
array[$i+1]=$tmp
changed=1
fi
done
done
echo "Sorted array: "
echo "${array[*]}"
Edit:
Thanks for answering my question. I have changed the code, and now and it looks something like this.
But unfortunately there is still a problem.
It says:
jdoodle.sh: line 3: $'\r': command not found
jdoodle.sh: line 8: syntax error near unexpected token `$'\r''
jdoodle.sh: line 8: ` for ((i=0;i<=${#array[#]}-1;i++))

Answer 1

This is one implementation of bubble sort:
#!/bin/bash
array=(5 3 2 1 4)
echo "${array[*]}"
size=${#array[#]}
for (( i=0; i<size-1; i++ )); do
for (( j=0; j<size-i-1; j++ )); do
if (( array[j] > array[j+1] )); then
tmp=${array[j]}
array[j]=${array[j+1]}
array[j+1]=$tmp
fi
done
done
echo "Sorted array:"
echo "${array[*]}"
Major problem with your code is that it actually does not use arrays.
Define arrays like array=(value1 value2 value3). It's also better to use [[ ]] for testing instead of [ ]. If we were to change your code just a little to also create a functioning bubble sort algorithm, it could look like this:
#!/bin/bash
array=(5 3 2 1 4)
echo "${array[*]}"
changed=1 j=0
while [[ $changed != 0 ]]
do
((j++))
changed=0
for (( i=0; i<${#array[#]}-j; i++ ))
do
if [[ ${array[i]} -gt ${array[i+1]} ]]
then
tmp=${array[i]}
array[i]=${array[i+1]}
array[i+1]=$tmp
changed=1
fi
done
done
echo "Sorted array:"
echo "${array[*]}"

Answer 2

I do not get the \r messages, even in your test environment; in general, they are a result of DOS/Windows combatability (with a b).
Since this is obviously a tutorial example (why else would someone do bubblesort), some remarks about the code.
array="5 3 2 1 4"
does not create the array that you want. It creates a string. What you are looking for is:
array=(5 3 2 1 4)
The last element of the array is ${#array[#]}-1. Element counting starts at 0. So your for-loop should be:
for (( i=0 ; i<=${#array[#]}-2 ; i++ ))
-2 because you're referencing ${array[$i+1]}, which would otherwise be outside the boundary.