Add usage to CatalogDownloadFiles. Refs #9585.

Code/Mantid/Framework/ICat/inc/MantidICat/CatalogDownloadDataFiles.h

@@ -52,9 +52,8 @@ namespace Mantid
       ~CatalogDownloadDataFiles(){}
       /// Algorithm's name for identification overriding a virtual method
       virtual const std::string name() const { return "CatalogDownloadDataFiles"; }
-    ///Summary of algorithms purpose
-    virtual const std::string summary() const {return "Downloads the given data files from the data server";}
-
+      /// Summary of algorithms purpose.
+      virtual const std::string summary() const { return "Downloads datafiles from the archives based on the ID of a datafile."; }
       /// Algorithm's version for identification overriding a virtual method
       virtual int version() const { return 1; }
       /// Algorithm's category for identification overriding a virtual method
@@ -69,7 +68,6 @@ namespace Mantid
       std::string testDownload(const std::string& URL,const std::string& fileName);
 
     private:
-      
       /// Overwrites Algorithm method.
       void init();
       /// Overwrites Algorithm method

Code/Mantid/docs/source/algorithms/CatalogDownloadDataFiles-v1.rst

@@ -9,8 +9,52 @@
 Description
 -----------
 
-This algorithm gets the location strings for the selected files from the
-data archive; if the data archive is not accessible, it downloads the
-files from the data server.
+This algorithm downloads a datafile or multiple datafiles based on the given ID of a datafile in an investigation. It first checks if the file can be downloaded from the data archives (based on information in the config file Facilities.xml) and downloads the file from there. Otherwise, the file is downloaded over HTTPS.
+
+The datafile ID to use to download a datafile can be obtained from :ref:`CatalogGetDataFiles <algm-CatalogGetDataFiles>`.
+
+Usage
+-----
+
+**Example - downloading a single datafile from ICAT.**
+
+.. code:: python
+
+    # Assuming you have previously logged into the catalog
+    # and stored the session return value in the variable 'session'
+    CatalogDownloadDataFiles(FileIds = '33127010', # Which file to find?
+                             FileNames = '33127010.nxs', # What to name it?
+                             DownloadPath = '~/Desktop',  # Where to save it?
+                             Session = session.getPropertyValue("Session") # Which session to use?
+                            )
+
+Output:
+
+.. code:: python
+
+    # Outputs a list locations of the datafiles downloaded.
+    # USERNAME will be your username on your system.
+    ['/home/USERNAME/Desktop/33127010.nxs']
+
+**Example - downloading multiple datafiles from ICAT.**
+
+.. code:: python
+
+    # The ids of the datafiles to download.
+    # These could be obtained from CatalogGetDataFiles or entered manually.
+    datafile_ids = [33127010, 33127011]
+
+    # This option will not append any file extensions to the datafiles.
+    CatalogDownloadDataFiles(FileIds = datafile_ids,    # We now pass our list of ids here
+                             FileNames = datafile_ids,  # and also here.
+                             DownloadPath = '~/Desktop',
+                             Session = session.getPropertyValue("Session")
+                             )
+
+Output:
+
+.. code:: python
+
+    ['/home/USERNAME/Desktop/33127010.nxs', '/home/USERNAME/Desktop/33127011.nxs']
 
 .. categories::