Jb / json.bash – Command-line tool (and bash library) that creates JSON
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…
In plain words
jb is a command-line tool and bash library that converts shell-native data—such as environment variables, files, and program output—into JSON format. Designed for both interactive use and scripts, it prioritizes robustness by treating values as strings by default, requiring explicit type annotations to parse other types, and avoiding silent errors or data coercion. It supports shell patterns like process substitution and null-terminated data, making it useful for developers who need safe, ergonomic JSON creation without exposing secrets through command arguments.
written from the facts on this page · September 2026
From the sources
In the maker’s words, at launch
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...
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