Remove a file or a folder from the Opal file system.
Examples
if (FALSE) { # \dontrun{
o <- opal.login('administrator','password', url='https://opal-demo.obiba.org')
# remove a file
opal.file_rm(o, '/home/administrator/export/some-data.csv')
# remove recursively a folder
opal.file_rm(o, '/home/administrator/export')
opal.logout(o)
} # }