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File Downloads from a GSAC Repository

One of the key services of a GSAC-enabled data repository is providing downloads of files of instrumental observation data files. GSAC relies on the agency running GSAC to provide the IT infrastructure (FTP) to serve file downloads, and to provide GSAC with the information about how to download files, typically a URL for each FTP file download.

A common case is, if you search a GSAC-enabled data repository for files (using the web page UI, the API, or the GSAC client) and specify result output format of "file.url," you will get a list of one or more URLs like this:

ftp://data-out.unavco.org/pub/rinex/obs/2012/158/palm1580.12d.Z

This is of course a URL which can be used to download a file with FTP from the given server. In the simplest case, the GSAC gets this complete URL as one field from the database. (In more complex cases, the information in the database is insufficient but the complete URL can be constructed from known information by GSAC. Such a case will require new Java coding to tell GSAC how to assemble disparate values into the appropriate URL for a file.

If you use output of "file.wget" the result is a file called "gsacwget.sh," a script file, with lines such as

wget ftp://data-out.unavco.org/pub/rinex/obs/2012/158/palm1580.12d.Z

Each line is a wget command to download one file with "wget" from the given server. GSAC constructs the wget lines using the FTP URLs.

Java Webstart File Downloader

An optional file download mechanism uses a Java Webstart based application that is used to download to your computer the results of a GSAC files query. It lists the FTP URLS and will download each file and place it in the specified Destination Directory.

Make local directories

Checking the Make local directories checkbox results in the downloader making subdirectories under the Destination Directory that correspond to the directory paths in the FTP URLs.

Overwrite files

Normally, if a file already exists on your computer then the downloader will not fetch a new one. You can control this behavior with the Overwrite files option.

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