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+= Multiline comments in POSIX sh
+:categories: sh
+
+:posixsh: https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.html#tag_19_07_04
+
+
+I realized one can use heredocs for multiline comments in sh:
+
+[source,sh]
+----
+cat <<'COMMENT' > /dev/null
+if wip; then
+	unfinished and broken syntax >
+fii
+COMMENT
+----
+
+
+...instead of:
+
+[source,sh]
+----
+# if wip; then
+#	unfinished and broken syntax >
+# fii
+----
+
+
+What is going on: the {posixsh}[language defines] `<<` as a redirect of the
+"here-document" type.  After `<<` you can put anything, and sh will use that as
+a token to look for on the following lines:
+
+[source,sh]
+----
+cat <<'bleh'
+...
+bleh
+----
+
+Make sure to include the `'quotes'` around the word, otherwise anything with a
+`$` would get replaced just like a `"double-quoted"` string.
+
+"bleh" works fine, like any word would.
+
+But that example left as-is would print the string to stdout.  To avoid that, we
+shove the contents to `/dev/null`.  So it isn't technically a comment, its more
+like a constant string that gets emitted and discarded.
+
+Sure its hacky, but at this point what in sh isn't?  It even supports nesting!
+
+[source,sh]
+----
+cat <<'COMMENT1' > /dev/null
+
+cat <<'COMMENT' > /dev/null
+
+# ... code ...
+
+COMMENT
+
+COMMENT1
+----
+
+
+I've never committed any code with this, just used while debugging sh code.
+Make sure to handle with care