jb is a UNIX tool that creates JSON, for shell scripts or interactive use. Its "one thing" is to get shell-native data (environment variables, files, program output) to somewhere else, using JSON encapsulate it robustly.

I wrote this because I wanted a robust and ergonomic way to create ad-hoc JSON data from the command line and scripts. I wanted errors to not pass silently, not coerce data types, not put secrets into argv. I wanted to leverage shell features/patterns like process substitution, environment variables, reading/streaming from files and null-terminated data.

If you know of the jo program, jb is similar, but type-safe by default and more flexible. jo coerces types, using flags like -n to coerce to a specific type (number for -n), without failing if the input is invalid. jb encodes values as strings by default, requiring type annotations to parse & encode values as a specific type (failing if the value is invalid).

If you know jq, jb is complementary in that jq is great at transforming data already in JSON format, but it's fiddly to get non-JSON data into jq. In contrast, jb is good at getting unstructured data from arguments, environment variables and files into JSON (so that jq could use it), but jb cannot do any transformation of data, only parsing & encoding into JSON types.

I feel rather guilty about having written this in bash. It's something of a boiled frog story. I started out just wanting to encode JSON strings from a shell script, without dependencies, with the intention of piping them into jq. After a few trials I was able to encode JSON strings in bash with surprising performance, using array operations to encode multiple strings at once. It grew from there into a complete tool. I'd certainly not choose bash if I was starting from scratch now...