Error on backup bash script: syntax error near unexpected token `newline' - bash

Question

I am having problem finding error on bash script for handling backup:daily, monthly, yearly. Here is the script:
#!/bin/bash
echo > /home/alpha/folder/keep.txt
#writing dates of the backups that should be kept to the array
for i in {0..7}; do ((keep[$(date +%Y%m%d -d "-$i day")]++)); done
for i in {0..4}; do ((keep[$(date +%Y%m%d -d "sunday-$((i+1)) week")]++)); done
for i in {0..12}; do
DW=$(($(date +%-W)-$(date -d $(date -d "$(date +%Y-%m-15) -$i month" +%Y-%m-01) +%-W)))
for (( AY=$(date -d "$(date +%Y-%m-15) -$i month" +%Y); AY < $(date +%Y); AY++ )); do
((DW+=$(date -d $AY-12-31 +%W)))
done
((keep[$(date +%Y%m%d -d "sunday-$DW weeks")]++))
done
for i in {0..30}; do
DW=$(date +%-W)
for (( AY=$(($(date +%Y)-i)); AY < $(date +%Y); AY++ )); do
((DW+=$(date -d $AY-12-31 +%W)))
done
((keep[$(date +%Y%m%d -d "sunday-$DW weeks")]++))
done
#writing the array to file keep.txt line by line
for i in ${!keep[#]}; do echo $i >> /home/alpha/folder/keep.txt; done
#delete all files that not mentioned in keep.txt
cd /home/alpha/folder
ls -1 /home/alpha/folder/ | sort /home/alpha/folder/keep.txt /home/alpha/folder/keep.txt - | uniq -u | xargs rm -rf
rm /home/alpha/folder/keep.txt
When I try to run the script, throws error message:
./back.sh: line 12: syntax error near unexpected token `newline' ./back.sh: line 12: ` done'
Where did I do wrong on the script?

Answer 1

Your date expression seems to misbehave inside the arithmetic context. Adding temporary variables solved your issue for me :
#!/bin/bash
echo > /home/alpha/folder/keep.txt
#writing dates of the backups that should be kept to the array
for i in {0..7}; do ((keep[$(date +%Y%m%d -d "-$i day")]++)); done
for i in {0..4}; do ((keep[$(date +%Y%m%d -d "sunday-$((i+1)) week")]++)); done
for i in {0..12}; do
DW=$(($(date +%-W)-$(date -d $(date -d "$(date +%Y-%m-15) -$i month" +%Y-%m-01) +%-W)))
begin=$(date -d "$(date +%Y-%m-15) -$i month" +%Y)
for (( AY=begin; AY < $(date +%Y); AY++ )); do
((DW+=$(date -d $AY-12-31 +%W)))
done
((keep[$(date +%Y%m%d -d "sunday-$DW weeks")]++))
done
for i in {0..30}; do
DW=$(date +%-W)
begin=$(($(date +%Y)-i))
for (( AY=begin; AY < $(date +%Y); AY++ )); do
((DW+=$(date -d $AY-12-31 +%W)))
done
((keep[$(date +%Y%m%d -d "sunday-$DW weeks")]++))
done
#writing the array to file keep.txt line by line
for i in ${!keep[#]}; do echo $i >> /home/alpha/folder/keep.txt; done
#delete all files that not mentioned in keep.txt
cd /home/alpha/folder
ls -1 /home/alpha/folder/ | sort /home/alpha/folder/keep.txt /home/alpha/folder/keep.txt - | uniq -u | xargs rm -rf
rm /home/alpha/folder/keep.txt
However, I am unsure why the expression misbehaves inside the arithmetic block.