Parameter Expansion
The `$' character introduces parameter expansion, command substitution, or arithmetic expansion. The parameter name or
symbol to be expanded may be enclosed in braces, which are optional but serve to protect the variable to be expanded
from characters immediately following it which could be interpreted as part of the name.
When braces are used, the matching ending brace is the first `}' not escaped by a backslash or within a quoted string,
and not within an embedded arithmetic expansion, command substitution, or parameter expansion.
${parameter}
The value of parameter is substituted. The braces are required when parameter is a positional parameter with
more than one digit, or when parameter is followed by a character which is not to be interpreted as part of its
name.
そう:hive -e 'set a=test_table; desc ${hiveconf:a};'