On most OS, shebangs can only specify a single parameter.

Problematic code:

#!/usr/bin/env bash -x

Correct code:

#!/usr/bin/env bash
set -x

Rationale:

Most operating systems, including POSIX, Linux and FreeBSD, allow only a single parameter in the shebang. The example is equivalent to calling env 'bash -x' instead of env 'bash' '-x', and it will therefore fail.

The shebang should be rewritten to use at most one parameter. Shell options can instead be set in the body of the script.

Exceptions

macOS X currently allows multiple words in the shebang. Scripts running on OSX exclusively can ignore this warning.