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Reading Data from ZIP Files

Problem

You have an archive in ZIP format and you want to access the files in the archive.

Solution

(require (planet "unzip.ss" ("dherman" "zip.plt" 2)))
(parameterize ([current-directory "output"])
  (with-input-from-file (build-path 'up "archive.zip") unzip))

Discussion

The zip.plt library in PLaneT has functionality for both unzipping an entire ZIP file or extracting individual entries. The above example unzips the entire contents of archive.zip to the output subdirectory of the current directory.

Here is an example that extracts a particular entry and saves it elsewhere:

(require (planet "unzip.ss" ("dherman" "zip.plt" 2)))
(require (lib "port.ss"))
(let ([zip-dir (read-zip-directory "archive.zip")])
  (unzip-entry "archive.zip"
               zip-dir
               #"subdir/document.txt"
               (lambda (name dir? in)
                 (with-output-to-file "local-copy.txt"
                   (copy-port in (current-output-port))))))

To extract an individual entry from a ZIP file, you first read its central directory with read-zip-directory, and then you extract the entry with unzip-entry. (Notice that entry names are specified with byte strings.)

See the PLaneT repository documentation for more information on the zip.plt library.

Comments about this recipe

Contributors

-- GordonWeakliem - 13 Aug 2004 -- DaveHerman - 22 Feb 2005