- file_reopen(+FileName,+Mode,+Stream,-RetCode)
-
Takes an existing I/O stream, closes it, then opens it and
attaches it to a file. This can be used to redirect I/O from any of the
standard streams to a file. For instance,
| ?- file_reopen('/dev/null', w, 3, Error).
redirects all warnings to the Unix black hole.
On success, RetCode is 0; on error, the return code is negative.
- file_clone(+SrcStream,?DestStream,-RetCode)
-
This is yet another way to redirect I/O. It is a Prolog interface to
the C dup and dup2 system calls. If DestStream is a
variable, then this call creates a new XSB I/O stream that is a clone
of SrcStream. This means that I/O sent to either stream goes
to the same place. If DestStream is not a variable, then it must
be a number corresponding to a valid I/O stream. In this case, XSB
closes DestStream and makes it into a clone of SrcStream.
For instance, suppose that 10 is a I/O Stream that is currently open
for writing to file foo.bar. Then
| ?- file_clone(10,3,_).
causes all messages sent to XSB standard warnings stream to go to file
foo.bar. While this could be also done with file_reopen,
there are things that only file_clone can do:
| ?- file_clone(1,10,_).
This means that I/O stream 10 now becomes clone of standard
output. So, all subsequent I/O will now go to standard output instead
of foo.bar.
On success, RetCode is 0; on error, the return code is negative.
- file_truncate(+Stream, +Length, -Return)
- file_io
The regular file referenced by the StreamStream
is chopped to have the size of Length bytes. Upon successful
completion Return is set to zero.
Portability Note: Under Windows (including Cygwin) file_truncate/2
is implemented using _chsize(), while on Unix ftruncate()
is used. There are minor semantic differences between these two
system calls, which are reflected by the behavior of file_truncate/2 on different platforms.
- tmpfile_open(-Stream)
-
Opens a temporary file with a unique filename. The file is deleted
when it is closed or when the program terminates.
