Index: library/mongodb/example-nsf-gridfs.tcl
===================================================================
diff -u -rdf67ed7db2b0cda881c4a9e704379a2a02d415b6 -r2fbf1bf87402e8639e772781c5719164e7e55555
--- library/mongodb/example-nsf-gridfs.tcl	(.../example-nsf-gridfs.tcl)	(revision df67ed7db2b0cda881c4a9e704379a2a02d415b6)
+++ library/mongodb/example-nsf-gridfs.tcl	(.../example-nsf-gridfs.tcl)	(revision 2fbf1bf87402e8639e772781c5719164e7e55555)
@@ -14,12 +14,16 @@
 #    $ mongo
 #    > use myfs
 #    > show collections
+#    > db.fs.files.find()
 #
 # or via the mongofiles interface:
 #
 #    $ mongofiles -d myfs list
 #
 
+#
+# First, as usual, open the connection to the mongo db
+#
 set mongoConn [::mongo::connect]
 
 #
@@ -29,12 +33,18 @@
 set gridFS [::mongo::gridfs::open $mongoConn myfs fs]
 
 #
-# The current version of gridfs_store_file() is quite unfriendly,
-# since it assumes that the file exists, and aborts otherwise. So, we
-# perform the existance test here. 
+# gridfs::remove_file removes all files with the specified name
+# multiple store operations create "revisions" with different uploadDates
+::mongo::gridfs::remove_file $gridFS README
+
 #
+# ::mongo::gridfs::store_file $gridFS $inputFileName $storeFileName text/plain
 # Note that the input file name can be "-" for reading from stdin.
 #
+# The current version of gridfs_store_file() is quite unfriendly,
+# since it assumes that the file exists, and aborts otherwise. So, we
+# perform the existence test here. 
+#
 # Store a known file:
 #
 set fn README
@@ -45,29 +55,63 @@
   puts stderr "no such file: $fn"
 }
 
-# unknown file
-set fn unknown-file
-if {[file readable $fn]} {
-  set r [::mongo::gridfs::store_file $gridFS $fn $fn text/plain]
-  puts stderr r=$r
-} else {
-  puts stderr "no such file: $fn"
-}
-
+#
+# Open a grid file, get some of its properties, and read it in chunks
+# of 500 bytes, and close it finally.
+#
 set f [mongo::gridfile::open $gridFS README]
-puts stderr "opened file $f"
-puts stderr meta=[mongo::gridfile::get_metadata $f]
-puts stderr contentlength=[mongo::gridfile::get_contentlength $f]
-puts stderr contenttype=[mongo::gridfile::get_contenttype $f]
+puts stderr "\nOpened grid file $f"
+puts stderr "Metadata: [mongo::gridfile::get_metadata $f]"
+puts stderr "ContentLength: [mongo::gridfile::get_contentlength $f]"
+puts stderr "ContentType: [mongo::gridfile::get_contenttype $f]"
 while {1} {
   set chunk [mongo::gridfile::read $f 500]
   puts stderr "read chunk-len [string length $chunk] content [string range $chunk 0 10]..."
-  if {[string length $chunk] < 500} break;
+  if {[string length $chunk] < 500} {
+    break
+  }
 }
 mongo::gridfile::close $f
-puts stderr OK
 
 #
+# Access the files stored in the gridfs via plain query interface
+#
+puts "\nAll Files:\n[join [::mongo::query $mongoConn myfs.fs.files {}] \n]\n"
+
+#
+# Get the file named README from the gridfs via plain query interface
+#
+set atts [lindex [::mongo::query $mongoConn myfs.fs.files \
+		      [list \$query object {filename string README}] \
+		      -limit 1] 0]
+puts "Attributes of file README:\n$atts\n"
+
+#
+# Extract the oid from the bson attributes
+#
+foreach {name type value} $atts {
+  if {$name eq "_id"} {
+    set oid $value
+    break
+  }
+}
+
+#
+# Add a dc:creator to the bson attributes ...
+#
+lappend atts metadata object {dc:creator string "Gustaf Neumann"}
+# .. and update the entry in the gridfs
+::mongo::update $mongoConn myfs.fs.files [list _id oid $oid] $atts
+
+#
+# Now we can use the gridfs interface to obtain the additional
+# metadata as well
+#
+set f [mongo::gridfile::open $gridFS README]
+puts stderr "Metadata: [mongo::gridfile::get_metadata $f]"
+mongo::gridfile::close $f
+
+#
 # close everything
 #
 ::mongo::gridfs::close $gridFS