Is it possible to open or query a named mutex, using OpenMutex, by its full path qualification? For example:
HANDLE hHandleMutex = OpenMutex(READ_CONTROL, FALSE,
"\\Sessions\\1\\BaseNamedObjects\\SmartScreen_AppRepSettings_Mutex");
However, the function returns NULL and fails with error 161 (ERROR_BAD_PATHNAME: The specified path is invalid). Yes, the documentation says well about \\Global and \\Local prefixes and doesn't state anything about these full object names. However, MSDN doesn't state everything!
I am aware that we can query the same using NtQuerySystemInformation, NtQueryObject undocumented APIs. But that involves opening process, duplicating the token etc. I can very well use these APIs, but wanted a simple solution.
Let's assume that process is running as a SYSTEM account, so error 5 (access denied) won't be a problem. If that's the problem, I can handle it.
You are using the wrong path. It should be:
"Session\\1\\SmartScreen_AppRepSettings_Mutex"
The documentation says that the Session\ prefix is "reserved for system" use. Caveat emptor.
Related
I looked up man page and everything I could find on the net, but I couldn't find details regarding the errors that are thrown for the LOOKUP op of namei() call (FreeeBSD). I even looked at the source code (kern/vfs_lookup.c). My question is, supposing as a typical user (non-root) I want to do a lookup operation on a file (say, 5 which is in /1/2/3/4/5), will the namei() throw EACCES or EPERM if the user doesn't have permissions (search or read or both) on atleast one of the components (say, 3) of the whole file path? namei() should error out EACCES right if there is no search or read perm on dir 3?
The rule is: if something was denied by permissions (as in, stuff you can set using chmod(1), or ACLs), you get EACCES. Otherwise, when you try something that does not depend on permissions, for example change file owner, you get EPERM.
I am trying to find a read that differentiates the advantages of using a Path object over the File object in java. I see a comparison of the API here http://docs.oracle.com/javase/tutorial/essential/io/legacy.html but don't really see the real advantages anywhere. Any pointer will be appreciated!
Generally one could say that both classes have different focus.
File is designed for file handling (creating, deleting, ...) while Path is focused on filename parsing.
File seems to have most functionality of Path included but there may be special cases where Path suits better.
Please see the documentation sites (especially methods overview) java.nio.File and java.nio.file.Path for further information.
What's the simplest way to find the path to the file in which I am "executing" some code? By this, I mean that if I have a file foo.py that contains:
print(here())
I would like to see /some/path/foo.py (I realise that in practice what file is "being executed" is complicated, but I think the above is well defined - a source file that contains some function that, when executed, gives the path to said file).
I have needed this in the past to make tests (that require some external file) self-contained, and I am currently wondering if it would be a useful way to locate some support files needed by a program. But I have never found a good way of doing this. The inspect module sounds like it should work, but you seem to need a class or function that is defined in that module.
In particular, the module instances contain __file__ attributes, but I can't see how to get the "current" module. Objects have a __module__ attribute, but that's the module name, not a module instance.
I guess one way is to throw and catch an exception and inspect the contents, but that seems like hard work. Surely there is a simple, easy way that I have missed?
To get the absolute path of the current file:
import os
os.path.abspath(__file__)
To get content of external file distributed with your package you could use pkg_util.get_data()(stdlib) or pkg_resources.resouce_string() (setuptools) to support execution from zip-archives or standalone executables created by py2exe, PyInstaller or similar, example.
Is there a built-in predicate or a easy way to remove from the knowledge database of prolog a source files that has already been consulted? I've gone through the reference manual and didn't find any thing that could do that.
You can do it with these procedures which use source_file/1 and source_file/2:
unload_last_source:-
findall(Source, source_file(Source), LSource),
reverse(LSource, [Source|_]),
unload_source(Source).
unload_source(Source):-
ground(Source),
source_file(Pred, Source),
functor(Pred, Functor, Arity),
abolish(Functor/Arity),
fail.
unload_source(_).
unload_source/1 abolishes all predicates defined by the input Source file name. Be warned that it needs to be an absolute path.
unload_last_source/0 will retrieve the last consulted file name and unload it.
After a file has been consulted, it become 'irrelevant' to Prolog. So I think that generally to answer should be no. But SWI-Prolog has a rich set of builtins that allows you to control your prolgram. For instance
?- [stackoverflow].
?- predicate_property(P, file('/home/carlo/prolog/stackoverflow.pl')).
P = yield(_G297, _G298) ;
P = now _G297 ;
P = x(_G297) ;
...
?- abolish(yield/2).
true.
?- predicate_property(P, file('/home/carlo/prolog/stackoverflow.pl')).
P = now _G297 ;
P = x(_G297) ;
...
Note that abolish doesn't require the file name to work, you could delete predicates loaded from other sources files.
clause, clause_property and erase should give more control, but I get an error I don't understand (it's undocumented) when attempting to use erase:
?- clause(strip_spaces(_G297, _G298),X,Y),erase(Y).
ERROR: erase/1: No permission to clause erase `<clause>(0x29acc30)'
if you know the name of the predicate, for example fact/2, you can use:
retractall(fact(_,_)).
This will work.
unload_file(+File)
Remove all clauses loaded from File. If File loaded a module, clear
the module's export list and disassociate it from the file. File is a
canonical filename or a file indicator that is valid for load_files/2.
This predicate should be used with care. The multithreaded nature of
SWI-Prolog makes removing static code unsafe. Attempts to do this
should be reserved for development or situations where the application
can guarantee that none of the clauses associated to File are active.
I'm attempting to build Firefox on my Windows Vista Ultimate machine. I keep getting the following error:
nsinstall: Bad file number
I've read that this error is caused because of UAC in Vista. Here are the two articles that lead me to this conclusion. https://wiki.mozilla.org/Penelope_Developer_Page#Windows_Vista and http://www.kevinbrosnan.net/mozilla-build-error-nsinstall-bad-file-number
Using the standard "Run as Administrator", I've attempted to redo my build but I get the exact same error. I also started a normal command prompt as admin and then went to the batch file in mozilla-build (start-msvc8.bat) and ran it. Still, same error at the same point.
Any other insights on how I might either get around this error or perhaps something else is causing the error?
Note: I also posted something here in the hopes to get topic-specific help but I've not heard a peep... After I posted that I found the info on nsinstall. Anyway, I prefer SO so I thought I'd try here...
Update: I've attempted to completly disable UAC to correct the problem as is suggested by cnemelkasr. I've received the exact same error. This new knowledge is making me think that a file or folder is missing... Does anyone who has experience with NSInstall know what the given error -- Bad file number -- might mean? I figure it might be referring to a file handle...
If it really is a UAC error, you can try turning off UAC altogether. I've had to do this for several packages. There are numerous places on the web to get the instructions for doing that.
http://www.petri.co.il/disable_uac_in_windows_vista.htm is one of them.
I found the answer to my question. I'm posting the answer here to share the answer with others and to close this question.
After disabling the UAC, it was suggested that the directory depth was interfering with NSInstall. I moved the folder from c:/Users/Frank/Documents/hg-repos/firefox-src-hgRepo/mozilla-fv-expirement/ to C:/mozilla-fv-expirement/. Cleaned all previous build attempts and finally redid my build (with UAC off) and I received a working debug binary.
The suggestion was posted at: mozilla.dev.builds
The "Bad file number" message in the cases I have seen, is caused by too many arguments passed to execvp (command, argv) (or similar) function. But only from some programs. An old bash, sh or a Borland/Watcom program in your PATH is an likely candidate.
So when you shorten the name of the build directory, the total size of the command line (that eventually gets passed to CreateProcess()) gets shorter. I don't think UAC has anything to do with this since I've seen this on Win-XP too. But it's a bit strange Mozilla would not use relative paths while building. I guess it uses some directory prefix value in it's makefiles (I've never tried building it).
If you look at the documentation for _execvp():
http://msdn.microsoft.com/en-us/library/3xw6zy53.aspx
E2BIG is one of the possible errno values:
The space required for the arguments and environment settings exceeds 32 KB.
Now, here is the strange part.
Fact 1:
On Visual-C/MingW (any version), strerror(EBADF) doesn't return "Bad file number" .
(it return "Bad file descriptor").
Fact 2:
On Borland's CBuilder 5.6 and Watcom 1.9 (these do not use the MSVC runtime), strerror(EBADF) does indeed return "Bad file number".
Theory:
Is possible that Borland, Watcom (and other CRTs too?) mixes up the meaning of E2BIG and EBADF. Did that make any sense? Someone please correct me if you have a better theory.
I'm a bit confused myself...
Conclusion: Either shorten the size of your environment (easiest) or shorten the command-line (not always easy).
--gv