File streams in the NTFS file system allow more that one sequence of data to be associated with a file. For example Microsoft uses them to store the extended Properties as seen in the last tab of file properties in Explorer.
J can read and write file streams:
load'files' 'test'fwrite jpath'~temp/test.txt' 4 'abc'fwrite jpath'~temp/test.txt:a' 3 '123'fwrite jpath'~temp/test.txt:b' 3 fread jpath'~temp/test.txt' test fread jpath'~temp/test.txt:a' abc fread jpath'~temp/test.txt:b' 123 load'dir' dir jpath'~temp' jbreak <dir> 01-May-08 07:37:16 1.ijx 583 28-Apr-08 02:10:38 fif.htm 3821 30-Apr-08 01:55:58 test.txt 4 01-May-08 07:38:03
Note that there is only one file test.txt listed.
The streams verb from the Streams script can list streams available for a file.