Created SC2164 (markdown)

SC2164.md

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+## Use cd ... || exit in case cd fails.
+
+### Problematic code:
+
+    cd generated_files
+    rm -r *.c
+
+### Correct code:
+
+    cd generated_files || exit
+    rm -r *.c
+
+### Rationale:
+
+`cd` can fail for a variety of reasons: misspelled paths, missing directories, missing permissions, broken symlinks and more.
+
+If/when it does, the script will keep going and do all its operations in the wrong direction. This can be messy, especially if the operations involve creating or deleting a lot of files. 
+
+You should therefore always check the condition of `cd`, either with `|| exit` as suggested, or things like `if cd somewhere; then ...; fi`.
+
+### Exceptions:
+
+ShellCheck does not give this warning when `cd` is on the left of a `||` or `&&`, or the condition of a `if`, `while` or `until` loop. Having a `set -e` command anywhere in the script will disable this message, even though it won't necessarily prevent the issue.
+
+If you are accounting for `cd` failures in a way shellcheck doesn't realize, you can disable this message with a [[directive]].