MIME Types for Nushell

MIME types, also known as media or content types, are used to identify data formats. Since Nushell is not officially recognized by the Internet Assigned Numbers Authority (IANA), all Nushell MIME types are prefixed with "x-" to indicate their unofficial status. Despite this, some tools still rely on MIME types to identify data formats.

The three MIME types we define and recommend for consistent use are:

  • application/x-nuscript: This type is used for Nushell scripts and is similar to application/x-shellscript for Bash scripts. The "application" type is used because these scripts can be executable if the correct shebang is included.
  • text/x-nushell: This is an alias for application/x-nuscript but emphasizes that the script is human-readable, similar to text/x-python.
  • application/x-nuon: This type is used for the NUON data format.

How Nushell uses these types

Nushell records the content type of some pipeline data in its metadata (the content_type field):

  • open sets application/x-nuscript for .nu files. When open parses a file with a from command (for example a .nuon, .json or .md file), the parsed value has no content type. With open --raw, the file's content type is kept.
  • to nuon sets application/x-nuon. Other to commands set their own types, e.g. to json sets application/json.
  • config nu --doc and view source (for a custom command) set application/x-nuscript.
{a: 1} | to nuon | metadata | get content_type
# => application/x-nuon
{a: 1} | save --force data.nuon
open --raw data.nuon | metadata | get content_type
# => application/x-nuon
open data.nuon | metadata | get content_type? | describe
# => nothing

The HTTP commands use these types too:

  • http post, http put and http patch send the content type from the metadata as the Content-Type header when --content-type is not given. So {a: 1} | to nuon | http post $url sends Content-Type: application/x-nuon.
  • http get (like the other http commands) parses a response with the from command that matches the subtype of its content type, ignoring an x- prefix. A response with Content-Type: application/x-nuon is therefore parsed with from nuon.

text/x-nushell is not set or recognized by Nushell itself.