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+## #!/bin/sh was specified, so ____ is not supported, even when sh is actually bash.
+
+The shebang indicates that the script works with `/bin/sh`, but you are using non-standard features that may not work with `/bin/sh`, **even if /bin/sh is actually bash**. Bash behaves differently when invoked as `sh`, and disabling support for the highlighted feature is one part of that.
+
+Specify `#!/usr/bin/env bash` to ensure that bash (or your shell of choice) will be used, or rewrite the script to be more portable.
+
+The Ubuntu wiki has [a list of portability issues](https://wiki.ubuntu.com/DashAsBinSh) and suggestions on how to rewrite them.
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