Returns a string after performing the specified
stream_command. The returned string depends
on the
stream_command performed
and can be the null string. Commands are available to:
Open a stream for reading, writing, or both
Close a stream at the end of an operation
Move the line read or write position within a persistent stream
(for example, a file)
Get information about a stream
If the method is unsuccessful, it returns an error message
string in the same form that the
description method uses.
For most error conditions, the additional information is in the form of
a numeric return code. This return code is the value of
ERRNO that
is set whenever one of the file system primitives returns with a
-1.
