Bash Read: Reading comma separated list, last element is missed

With read, -d is used to terminate the input lines (i.e. not to separate input lines). Your last "line" contains no terminator, so read returns false on EOF and the loop exits (even though the final value was read).

echo '0,1,2,3,4,5' | { while read -d, i; do echo "$i"; done; echo "last value=$i"; }

(Even with -d, read also uses $IFS, absorbing whitespace including the trailing \n on the final value that would appear using other methods such as readarray)

The Bash FAQ discusses this, and how to handle various similar cases:

• Bash Pitfalls #47 IFS=, read [...]
• BashFAQ 001 How can I read a file [...] line-by-line
• BashFAQ 005 How can I use array variables?

As other answers state, -d is an end-of-line character, not a field separator. You can do

IFS=, read -a fields <<< "1,2,3,4,5"
for i in "${fields[@]}"; do echo "$i"; done

From man:

-d delim

The first character of delim is used to terminate the input line, rather than newline.

Your element 5 doesn't have a delimiter (comma), so it won't be read.