Add Turn A List From A Command Into JSON as a jq TIL

jq/turn-a-list-from-a-command-into-json.md

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+# Turn A List From A Command Into JSON
+
+There are a lot of command-line utilities that produce a list of things. Since
+JSON is a universal data format, it would be useful to be able to quickly turn
+some items from `stdout` into a JSON list.
+
+The [`jq`](https://jqlang.github.io/jq/) utility can help with this.
+
+Let's say I'm working with the following `git` command that lists changed files
+in a specific directory.
+
+```bash
+$ git diff --name-only | grep some/dir
+```
+
+I can then pipe that list of files to `jq` with a few flags.
+
+```bash
+$ git diff --name-only \
+  | grep some/dir \
+  | jq -R -s 'split("\n")[:-1]'
+```
+
+Here's what is going on:
+
+- The `-R` flag tells `jq` to accept raw input, rather than looking for JSON.
+- The `-s` flag is short for `--slurp` and tells `jq` to read in the entire
+  input before applying the filter.
+- The string argument is the filter to be applied to the output. It splits on
+  newlines and then takes the entire array except for the last item (`[:-1]`)
+  which would be an empty string for the trailing newline.
+- `jq` automatically turns the whole thing into a formatted JSON list.