$ cue help inputs
Many commands apply to a set of inputs:

cue <command> [inputs]

The list [inputs] may specify CUE packages, CUE files, non-CUE
files or some combinations of those. An empty list specifies
the package in the current directory, provided there is a single
named package in this directory.

CUE packages are specified as an import path. An import path
that is a rooted path --one that begins with a "." or ".."
element-- is interpreted as a file system path and denotes the
package instance in that directory.

Otherwise, the import path P denotes an external package found
in cue.mod/{pkg|gen|usr}/P.

An import path may contain one or more "..." to match any
subdirectory: pkg/... matches all packages below pkg, including
pkg itself, while foo/.../bar matches all directories named bar
within foo. In all cases, directories containing cue.mod
directories are excluded from the result.

Directory and file names that begin with "." or "_" are ignored,
unless explicitly listed as inputs.

A package may also be specified as a list of .cue files.
The special symbol '-' denotes stdin or stdout and defaults to
the cue file type for stdin. For stdout, the default depends on
the cue command. A .cue file package may not be combined with
regular packages.

Non-cue files are interpreted based on their file extension or,
if present, an explicit file qualifier (see the "filetypes"
help topic). By default, all recognized files are unified at
their root value. See the "filetypes" and "flags" help topics
on how to treat each file individually or how to combine them
differently.

If a data file has multiple values, such as allowed with JSON
Lines or YAML, each value is interpreted as a separate file.

If the --schema/-d is specified, data files are not merged, and
are compared against the specified schema within a package or
non-data file. For OpenAPI, the -d flag specifies a schema name.
For JSON Schema the -d flag specifies a schema defined in
"definitions". In all other cases, the -d flag is a CUE
expression that is evaluated within the package.

Examples (also see also "flags" and "filetypes" help topics):

# Show the definition of each package named foo for each
# directory dir under path.
$ cue def ./path/.../dir:foo

# Unify each document in foo.yaml with the value Foo in pkg.
$ cue export ./pkg -d Foo foo.yaml

# Unify data.json with schema.json.
$ cue export data.json schema: schema.json