Executes a system command. When the os attribute is specified, then the command is only executed when Ant is run on one of the specified operating systems.
The files and/or directories of a number of FileSets are passed as arguments to the system command.
If you specify a nested mapper and the dest attribute, the timestamp of each source file is compared to the timestamp of a target file which is defined by the nested mapper element and searched for in the given dest.
At least one fileset is required, and you must not specify more than one mapper.