SC2229

This does not read foo. Remove $/${} for that, or use ${var?} to quiet.

Problematic code:

read $foo

Correct code:

read foo

Rationale:

read takes a variable name, but shellcheck has noticed that you give it an expanded variable instead. This will populate whatever the variable expans to instead of the variable itself. For example:

foo=bar
read $foo   # Reads data into 'bar', not into 'foo'
read foo    # Reads data into 'foo'

Exceptions:

If this is intentional and you do want to read a variable through an indirect reference, you can silence this warning with a directive:

# shellcheck disable=SC2229
read "$foo"

Or take advantage of the fact that ShellCheck only warns when no parameter expansion modifiers are applied:

read "${foo}"    # ShellCheck warns
read "${foo?}"   # No warning

${foo?} fails when foo is unset, which is fine since read would have failed too. The main side effect is an improved runtime error message in that case.

Related resources:

• Bash Pitfalls #12: read $foo