On this page:
untgz

8 tar+gzip File Extraction

 (require file/untgz) package: base
The file/untgz library provides a function to extract items from a possible gzipped TAR/USTAR archive.

procedure

(untgz in    
  [#:dest dest-path    
  #:strip-count strip-count    
  #:filter filter-proc])  void?
  in : (or/c path-string? input-port?)
  dest-path : (or/c path-string? #f) = #f
  strip-count : exact-nonnegative-integer? = 0
  filter-proc : 
(path? (or/c path? #f)
 symbol? exact-integer? (or/c path? #f)
 exact-nonnegative-integer?
 exact-nonnegative-integer?
 . -> . any/c)
   = (lambda args #t)
The same as untar, but if in is in gzip form, it is gunzipped as it is unpacked.