( is invalid here. Did you forget to escape it?

Problematic code:

echo (foo) bar

Correct code:

Depends on your intention:

echo "(foo) bar"  # Literal parentheses
echo "$(foo) bar" # Command expansion
echo "foo bar"    # Tried to use parentheses for grouping or function invocation

Rationale:

ShellCheck expected an ordinary shell word but found an opening parenthesis instead.

Determine what you intended the parenthesis to do and rewrite accordingly. Common issues include:

• Wanting them to be literal, as in echo (FAIL) Some tests failed. In this case, it requires quoting.
• Wanting command expansion, as in echo Today is (date). Add the missing $: echo "Today is $(date)"
• Adding parentheses because other languages need them in that context, such as foo (bar, 42) to call a function. This should be foo bar 42. Also, shells do not support tuples or passing arrays as single parameters.

Exceptions:

Bash allows some parentheses as part of assignment-like tokens to certain commands, including export and eval. This is a workaround in Bash to allow commands that normally would not be valid:

eval foo=(bar)       # Valid command
echo foo=(bar)       # Invalid syntax
f=foo; eval $f=(bar) # Also invalid

In these cases, please quote the command, such as `eval "foo=(bar)". This does not change the behavior, but stops relying on bash specific parsing quirks.

Related resources:

• Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!