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get_stream_info(+Stream, ?Attr, -Value)
Succeeds if the attribute Attr of the open stream Stream has the value
Value.
- Stream
- Atom or integer denoting an open stream.
- Attr
- Atom or variable.
- Value
- Variable, atom, string or integer.
Description
Used to retrieve information associated to an open stream. The
available attributes and their meanings are:
Attr Value Description
aliases integer current number of symbolic names
compress on, off a hint for output operations (e.g.
write_exdr/2) to use a more compact
output format (output streams only).
Default: on (file,pipe,socket) or off.
connection atom identification of the connected
socket - file name for unix sockets,
host name for internet ones
device file, null, the device behind the stream
pipe, queue,
socket, tty,
string
end_of_line lf, crlf which end-of-line sequence to write
(output streams only)
event atom or event on writing to empty stream
event handle (see open/4)
fd integer the associated OS/UNIX file descriptor
flush flush, explicit or implicit flushing
end_of_line (output streams only)
last_written integer character code of last written character
(output streams only)
line integer current line number
(input streams only)
mode read, write, the stream's direction
update
name atom or associated filename, or contents
string (in case of a string or queue), or
pseudo file name (user, error, null)
macro_expansion on, off expand term macros (input streams only)
offset integer current position in the
stream, as given by at/2
output_options list default output options for all term
output on this stream. The list
format is as in write_term/2,3.
physical_stream integer associated stream number
port integer port number associated with an
internet socket
prompt string prompt string (input streams only)
prompt_stream integer output stream for the prompt
(input streams only)
sigio on SIGIO signals enabled (UNIX only)
system_use on, off a system stream is currently
redirected to this stream
usable on, off if the stream can currently be used:
flushing or reading the empty stream
may not be properly handled if `off'.
yield on, off yield on end-of-file (see open/4)
Modes and Determinism
- get_stream_info(+, -, -) is multi
- get_stream_info(+, +, -) is semidet
Fail Conditions
Fails if the requested attribute is not available for this stream
Exceptions
- (4) instantiation fault
- Stream is not instantiated.
- (5) type error
- Stream is neither an atom nor an integer.
- (5) type error
- Attr is instantiated, but not to an atom.
- (5) type error
- Value is instantiated, but not to an atom, string or integer.
- (6) out of range
- Attr is an atom, but not a valid attribute name.
- (193) illegal stream specification
- Stream does not denote an open stream.
Examples
Success:
[eclipse]: get_stream_info(input,X,Y), writeln(X is Y), fail.
name is user
physical_stream is 0
aliases is 2
system_use is on
line is 1
offset is 0
prompt is
prompt_stream is 1
fd is 0
reprompt_only is off
device is tty
mode is read
usable is on
macro_expansion is on
no (more) solution.
[eclipse]: get_stream_info(toplevel_input, prompt, P).
P = "\t"
yes.
Fail:
get_stream_info(output, prompt, P).
get_stream_info(output, system_use, off).
Error:
get_stream_info(X, Y, Z). (Error 4)
get_stream_info(file(f), Y, Z). (Error 5)
get_stream_info(output, 7, X). (Error 5)
get_stream_info(output, offset, 8.5). (Error 5)
get_stream_info(output, length, Z). (Error 6)
get_stream_info(nostream, Y, Z). (Error 193)
See Also
set_stream_property / 3, open / 3, open / 4, current_stream / 1, get_stream_info / 3, get_stream / 2, at / 2, write_term / 2, write_term / 3