Escaping characters in bash (for JSON)

Question

I'm using git, then posting the commit message and other bits as a JSON payload to a server. Currently I have: ``` MSG=`git log -n 1 --format=oneline | grep -o ' .\+'` ``` which sets MSG to something like: ``` Calendar can't go back past today ``` then ``` curl -i -X POST \ -H 'Accept: application/text' \ -H 'Content-type: application/json' \ -d "{'payload': {'message': '$MSG'}}" \ 'https://example.com' ``` My real JSON has another couple of fields. This works fine, but of course when I have a commit message such as the one above with an apostrophe in it, the JSON is invalid. How can I escape the characters required in bash? I'm not familiar with the language, so am not sure where to start. Replacing `'` with `\'` would do the job at minimum I suspect.

Accepted Answer

OK, found out what to do. Bash supports this natively as expected, though as always, the syntax isn't really very guessable!

Essentially `${string//substring/replacement}` returns what you'd image, so you can use

```
MSG=${MSG//\'/\\'}
```

To do this. The next problem is that the first regex doesn't work anymore, but that can be replaced with

```
git log -n 1 --pretty=format:'%s'
```

In the end, I didn't even need to escape them. Instead, I just swapped all the ' in the JSON to ". Well, you learn something every day.

Escaping characters in bash (for JSON)

Solution

Problem