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(or "In dash, ... is not supported." when using dash)
Problematic code:
#!/bin/sh
name="PATH"echo"${!name}"
Correct code:
The easiest solution is to switch to a shell that does support indirect expansion, like bash:
#!/bin/bash
name="PATH"echo"${!name}"
Alternatively, carefully rewrite using eval:
#!/bin/sh
name=PATH
eval"echo \"\$$name\""
Rationale:
Indirection expansion is an extension in bash and ksh, and not supported in dash or POSIX sh. Either switch to a shell that supports them, or write around it with careful use of eval. Take care to validate the variable name to avoid fragility and code injection.
Exceptions:
If you only intend to target shells that supports this feature, you can change
the shebang to a shell that guarantees support, or ignore this warning.
You can use # shellcheck disable=SC3000-SC4000 to ignore all such compatibility
warnings.
Related resources:
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