The cue command can log various summary statistics about each evaluation it performs, in order to assist with the diagnosis of performance-related and other issues. The command logs statistics when the CUE_STATS_FILE environment variable is set to a filename.

The filename is interpreted through the same rules that cue export applies to its --outfile argument, which are explained in cue filetypes. Statistics for each evaluation are written into the named file using the file’s implied data format. The file is overwritten on each cue invocation, without confirmation.

$ export CUE_STATS_FILE=stats.cue
$ cue vet someFile.cue
$ cat stats.cue
CUE: {
	Unifications: 4
	Disjuncts:    4
	Conjuncts:    4
	Freed:        4
	Reused:       2
	Allocs:       2
	Retained:     0
Go: {
	AllocBytes:   4458504
	AllocObjects: 49721

Specifying the filename - causes cue to log statistics to its standard error stream as JSON. A different format may be selected using a qualifier prefix as outlined in cue filetypes. For example: to emit YAML, specify yaml:-.