new file: shell/printing-json.md

shell/printing-json.md

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+# Printing JSON in the Shell
+
+Printing json might seem straightforward at first, just:
+
+```shell
+$ echo '{"name": "jes", "sign": "aquarius"}'
+# {"name": "jes", "sign": "aquarius"}
+```
+
+but inevitably, variables show up:
+
+```shell
+$ echo '{"name": "$name", "sign": "$sign"}'
+# {"name": "$name", "sign": "$sign"} <-- this output is very broken
+```
+
+We can instead use `printf`! `printf` offers several advantages over echo:
+
+- many languages (C, Go) have a `printf` equivalent, so it feels familiar
+- `printf` behavior does not differ across systems (it is posix compliant)
+- `printf` handles escape sequences (`printf "hello\nworld\n"`)
+- `printf` can trivially handle json
+
+Printing the same json text using `printf`:
+
+```shell
+$ printf '{"name": "%s", "sign": "%s"}' "$name" "$sign"
+# {"name": "jes", "sign": "aquarius"}
+```
+
+[source](https://j3s.sh/thought/shell-tip-print-json-with-printf.html)