How to extract the first sh code block from a Markdown file?

[ruzickap]

Hello

What is the best way to extract the first sh code block from this file?

Example:

cat > my_file.md <<\EOF
# My file with code

```bash
uname -a
```

```sh
pwd
```

```sh
ls -la
```
EOF

-> The expected output is pwd.

I tried mq commands like the following, but none of them work:

• mq 'select(.code.lang == "sh").[1]' my_file.md
• mq 'select(.code.lang == "sh") | .[1]' my_file.md
• mq 'select(.code.lang == "sh") | first' my_file.md

Thank you...

[harehare]

Hi! You can extract the first sh code block using:

mq -A 'filter(fn(n): n | .code.lang == "sh";) | first()' my_file.md
mq -A 'filter(fn(n): n | .code.lang == "sh";)[0]' my_file.md

The -A flag aggregates all nodes into a single array, then filter selects for sh blocks, and first() returns the first one.
However, I feel that the current syntax is a bit cumbersome, so I’m considering ways to make it easier to use in the future.

[ruzickap]

Thank you - it works :-)

[luckman212]

@harehare is there any practical difference between the following 4:

mq -A 'pluck(.code("sh").value)'
mq 'select(.code.lang == "sh") | .value'
mq 'select(.code.lang == "sh") | to_text()'
mq '.code | select(.code.lang == "sh") | .value'

Which would be the preferred/canonical form?

[harehare]

Sorry for the late reply!

All four work, but they differ slightly. .value returns the raw node, to_text gives you a plain string, and -A 'pluck(...)' processes the whole document as an array.

For this use case, the shortest and most straightforward option is:
mq '.code("sh").value'

[luckman212]

Great, that's what I ended up settling on anyway. Thank you 🙏