The following predicates form a simple access mechanism to the Unix
termcap library to provide terminal-independent I/O for screen
terminals. These predicates are only available on Unix machines. The
SWI-Prolog Windows console accepts the ANSI escape sequences.
- tty_get_capability(+Name,
+Type, -Result)
- Get the capability named Name from the termcap library. See
termcap(5) for the capability names. Type specifies the type
of the expected result, and is one of
string, number
or
bool. String results are returned as an atom, number
results as an integer, and bool results as the atom on or off.
If an option cannot be found, this predicate fails silently. The results
are only computed once. Successive queries on the same capability are
fast. This predicate can raise several exceptions if the terminal
environment is incomplete, notably if the environment variable TERM
does not exist or there is no matching entry in the termcap database.
- tty_goto(+X,
+Y)
- Goto position (X, Y) on the screen. Note that the
predicates
line_count/2
and line_position/2
will not have a well-defined behaviour while using this predicate.
- tty_put(+Atom,
+Lines)
- Put an atom via the termcap library function tputs(). This
function decodes padding information in the strings returned by tty_get_capability/3
and should be used to output these strings. Lines is the
number of lines affected by the operation, or 1 if not applicable (as in
almost all cases).
- tty_size(-Rows,
-Columns)
- Determine the size of the terminal. Platforms:
- Unix
- If the system provides ioctl calls for this, these are used and tty_size/2
properly reflects the actual size after a user resize of the window. The ioctl
is issued on the file descriptor associated with the
user_input
stream. As a fallback, the system uses tty_get_capability/3
using li and co capabilities. In this case the
reported size reflects the size at the first call and is not updated
after a user-initiated resize of the terminal.
- Windows
- Getting the size of the terminal is provided for swipl-win.exe.
The requested value reflects the current size. For the multithreaded
version the console that is associated with the
user_input stream is used.
