toml-cli

This is the home of the toml command, a simple CLI for editing and querying TOML files.

The intent of the toml command is to be useful

• in shell scripts, for consulting or editing a config file;
• and in instructions a human can follow for editing a config file, as a command to copy-paste and run.

A source of inspiration for the interface is the git config command, which serves both of these purposes very well without knowing anything about the semantics of Git config files -- only their general structure.

A key property is that when editing, we seek to preserve formatting and comments -- the only change to the file should be the one the user specifically asked for. To do this we rely on the toml_edit crate, which also underlies cargo-edit. There are a few edge cases where toml_edit can rearrange an oddly-formatted file (described in the toml_edit documentation); but for typical TOML files, we maintain this property with perfect fidelity.

The command's status is experimental. The current interface does not yet serve its purposes as well as it could, and incompatible changes are anticipated.

Usage

Reading: toml get

To read specific data, pass a TOML path: a sequence of path segments, each of which is either:

• .KEY, to index into a table or inline-table, or
• [INDEX], to index into an array-of-tables or array.

$ toml get Cargo.toml dependencies.serde
"1.0"

Data is emitted by default as JSON:

$ toml get Cargo.toml bin[0]
{"name":"toml","path":"src/main.rs"}

If you need a more complex query, consider a tool like jq, with toml simply transforming the file to JSON:

$ toml get pyoxidizer.toml . | jq '
    .embedded_python_config[] | select(.build_target | not) | .raw_allocator
  ' -r
jemalloc

(The TOML path . is an alias for the empty path, describing the whole file.)

Writing (ish): toml set

To edit the data, pass a TOML path specifying where in the parse tree to put it, and then the data value to place there:

$ cat >foo.toml <<EOF
[a]
b = "c"
EOF

$ toml set foo.toml x.y z
[a]
b = "c"

[x]
y = "z"

This subcommand is quite raw in two respects:

• We don't actually edit the file; we only print out the new version.
• The value to be set must be a string; input of booleans, arrays, etc. is unimplemented.

Reference

Base command toml

$ toml --help
toml-cli 0.2.0
A simple CLI for editing and querying TOML files.

USAGE:
    toml <SUBCOMMAND>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

SUBCOMMANDS:
    get     Print some data from the file
    help    Prints this message or the help of the given subcommand(s)
    set     Edit the file to set some data (currently, just print modified version)

toml get

$ toml get --help
toml-get 0.2.0
Print some data from the file

USAGE:
    toml get [FLAGS] <path> <query>

FLAGS:
    -h, --help           Prints help information
        --output-toml    Print as a TOML fragment (default: print as JSON)
    -V, --version        Prints version information

ARGS:
    <path>     Path to the TOML file to read
    <query>    Query within the TOML data (e.g. `dependencies.serde`, `foo[0].bar`)

toml set

$ toml set --help
toml-set 0.2.0
Edit the file to set some data (currently, just print modified version)

USAGE:
    toml set <path> <query> <value-str>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

ARGS:
    <path>         Path to the TOML file to read
    <query>        Query within the TOML data (e.g. `dependencies.serde`, `foo[0].bar`)
    <value-str>    String value to place at the given spot (bool, array, etc. are TODO)