Using “$RANDOM” to generate a random string in Bash

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Use parameter expansion. ${#chars} is the number of possible characters, % is the modulo operator. ${chars:offset:length} selects the character(s) at position offset, i.e. 0 – length($chars) in our case.

chars=abcd1234ABCD
for i in {1..8} ; do
    echo -n "${chars:RANDOM%${#chars}:1}"
done
echo

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