Command line

The vexy-json program reads relaxed JSON from files or standard input and writes standard JSON. It is built from the vexy-json-cli crate.

vexy-json [OPTIONS] [FILE]...

With no FILE, the program reads standard input. With several files, it processes them one after another (or in parallel with --parallel) and writes each result in turn.

How a run works

For each input, vexy-json:

1. Reads the bytes and checks that they are valid UTF-8. Invalid UTF-8 is an error that names the byte where decoding stopped.
2. Parses the text. It first tries a strict JSON parser (serde_json) and, if that fails, the forgiving Vexy JSON parser with the options from the command line.
3. On success, formats the value and writes it to standard output or to the --output file.
4. On failure, prints Error: and the message to standard error and exits with status 1. With --repair, it first tries to close truncated input (see Repairing incomplete input).

Output options

Option	Effect
-o, --output <FILE>	Write the result to FILE instead of standard output
-p, --pretty	Indent the output
--indent <INDENT>	Spaces per indentation level (default 2)
-c, --compact	Write everything on one line with no extra whitespace
-v, --validate	Check the input and print Valid JSON instead of the value

Without --pretty or --compact, objects and arrays are indented and scalars (strings, numbers, booleans, null) are written on one line. No newline is added after the output.

With --validate and more than one file (or in watch mode), each line names the file: settings.conf is valid JSON.

Syntax options

Each flag switches off one extension. They map to the parser options of the same name.

Flag	Disables
--no-comments	//, # and /* … */ comments
--no-trailing-commas	trailing commas
--no-unquoted-keys	unquoted object keys
--no-single-quotes	single-quoted strings
--no-implicit-top-level	objects and arrays without outer braces or brackets
--no-newline-as-comma	newlines as separators
--max-depth <MAX_DEPTH>	maximum nesting depth (default 128)

Input modes

Option	Effect
--ndjson	Treat the input as newline-delimited JSON: one value per line
--parallel-parse	Parse one large input with the parallel parser
--chunk-size <CHUNK_SIZE>	Minimum chunk size in bytes for parallel parsing (default 65536)
--max-threads <MAX_THREADS>	Thread limit for parallel parsing; 0 means automatic (default 0)
-j, --parallel	Process several input files at the same time
-w, --watch	Process the files, then reprocess each one when it changes
--lms	Run lms ls --json --llm and parse its output

--chunk-size and --max-threads apply to both --parallel-parse and --ndjson.

In --ndjson mode each value is written separately. With --pretty, values are separated by a blank line.

--watch needs at least one file. It prints Watching N files for changes... (Press Ctrl+C to stop) and keeps running until you stop it.

--lms is for the LM Studio command-line tool. It runs lms ls --json --llm, captures the complete output in a temporary file (256 MiB at most) and parses it. It cannot be combined with file arguments, --watch, --parallel, --repair, --parallel-parse or --ndjson.

Error and repair options

Option	Effect
--verbose-errors	Report the line and column of a parse error and show the lines around it
-r, --repair	Close input that ends inside open objects or arrays, and warn about it
--repair-details	Requires --repair; the repair report is the same as with --repair alone
--fallback	Accepted for compatibility; the strict-then-forgiving fallback always runs

--repair cannot be combined with --watch, --ndjson or --parallel-parse.

Examples

Parse a file and pretty-print it with four-space indentation:

vexy-json --indent 4 config.json5

Write the normalized, compact result to a new file:

vexy-json -c settings.conf -o settings.json

Check several files at once:

vexy-json -v a.conf b.conf

a.conf is valid JSON
b.conf is valid JSON

Find the line of a syntax error:

vexy-json --verbose-errors bad.conf

Error:
Parse error in file 'bad.conf' at line 4, column 9: Expected , or ] or newline but found Some((Colon, Span { start: 36, end: 37 })) at position 37

   3     list: [1, 2
   4 >   other: 3
              ^
   5   }

Without --verbose-errors the message is one line: bad.conf: Expected , or ] or newline … at position 37.

Reject anything that is not strict JSON:

vexy-json --no-comments --no-trailing-commas --no-unquoted-keys \
  --no-single-quotes --no-implicit-top-level --no-newline-as-comma data.json

Exit status

Status	Meaning
0	All inputs parsed (or were empty)
1	A file was missing, the input was not UTF-8, parsing failed or a repair was unsafe
2	Invalid command-line arguments, such as --repair together with --ndjson

Other options

Option	Effect
-h, --help	Print help; -h prints a summary
-V, --version	Print the version