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yap-6.3/packages/clib/streaminfo.pl
Vítor Santos Costa 40febfdf9b clib package
2010-06-17 00:40:25 +01:00

86 lines
2.9 KiB
Prolog

/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 2009, University of Amsterdam
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(stream_info,
[ stream_info/1 % +Stream
]).
:- use_foreign_library(foreign(streaminfo)).
%% stream_info(+Stream) is det.
%
% Print detailed information about a stream or a file-number to
% the error output. The output of this command is meant for
% experts and requires knowledge about the implementation of
% streams. It has been added to diagnose leaking streams in
% web-servers. For example, on linux systems we can examine
% process file-descriptors using
%
% ==
% % ls -l /proc/<pid>/fd
% ==
%
% If now (say) descriptor 15 is open where it should not be, we
% can this command to find the associated Prolog streams and print
% as mush as possible information about the stream.
%
% ==
% ?- stream_info(15).
% ==
%
% @param Stream A stream-handle, alias name or (integer) system
% file handle.
stream_info(Stream) :-
is_stream(Stream), !,
forall(stream_property(Stream, P),
print_property(P)),
nl,
catch('$stream_info'(Stream), E, true),
( nonvar(E)
-> format('~w:~t~25|~q~n', ['pending exception', E])
; true
).
stream_info(FileNo) :-
integer(FileNo), !,
findall(S, stream_property(S, file_no(FileNo)), Streams),
length(Streams, Len),
format('File no ~w is connected to ~d streams~n', [FileNo, Len]),
forall(member(Stream, Streams),
( format('****************~nStream ~p:~n', [Stream]),
stream_info(Stream))).
print_property(P) :-
P =.. [Name,Value], !,
format('~w:~t~25|~q~n', [Name, Value]).
print_property(input) :- !.
print_property(output) :- !.
print_property(P) :-
format('~p~n', [P]).