Created SC2217 (markdown)

SC2217.md

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+## Redirecting to 'echo', a command that doesn't read stdin. Bad quoting or missing xargs?
+
+### Problematic code:
+
+```sh
+echo << eof
+  Hello World
+eof
+```
+
+### Correct code:
+
+```sh
+cat << eof
+  Hello World
+eof
+```
+
+### Rationale:
+
+You are redirecting to one of several commands that don't read from stdin.
+
+This may happen when:
+
+* Confusing one command for another, e.g. using `echo` where `cat` was intended.
+* Incorrectly quoting angle brackets, e.g. using `echo <p>Hello` which tries to read from a file `p`.
+* Missing `xargs`, e.g. `mv -t dir < files` instead of `xargs mv -t dir < files` (or more safely, `tr '\n' '\0' < files | xargs -0 mv -t dir`), because stdin should be passed as parameters.
+
+Check your logic, and rewrite the command so data is passed correctly.
+
+### Exceptions:
+
+If you've overridden a command to return output, you can either rename it to make this obvious, or [[ignore]] this message.