I have a very difficult problem with a ros2 topic that for some reason keeps more than one message. My project is rather simple: I have a planner in which I can create targets and edit them. The planner consists of several nodes, one for changing each value of the target. List of my nodes:
/add_target
/change_comment
/change_target_index
/clear_state
/remove_target
/rename_target
/set_target
/toggle_select_target
/toggle_visible
Each node extends StateNode (see implementation below), which helps to keep the same state for each node.
The idea is simple: a node receives a service call, for example /planner/rename_target, finds the specific target from the node's state, modifies it, and publishes new state to /planner/state. Each node is subscribed to /planner/state and sets the state to the message received. The idea is to keep the state consistent across all nodes, so each node has access to all state data and can modify it.
I have set my quality of service profile to keep ONLY the latest message. However, my problem is that after using service calls to different nodes, sometimes when running for example
ros2 topic echo --qos-history keep_last --qos-depth 1 --qos-durability transient_local --qos-reliability reliable /planner/state
I receive multiple messages. The order of the messages changes randomly. The state of each node seems to be the same, BUT it seems there are old messages "floating around" in the topic. My qos should allow only the latest message to persist.
For example, if I first service call twice
ros2 service call /planner/add_target mtms_interfaces/srv/AddTarget "{target: {position:{x: 0.0,y: 0.0,z: 0.0}, orientation: {alpha: 0.0,beta: 0.0,gamma: 0.0}}}"
my topic echo looks normal, but if I then
ros2 service call /planner/rename_target mtms_interfaces/srv/RenameTarget "{name: 'Target-0', new_name: 'example'}"
suddenly my topic echo shows two messages. In one of the messages the target has not been modified, and in the other the target has been modified.
What could be the problem here?
Here are some examples of my nodes
StateNode implementation:
class StateNode(Node):
def __init__(self, name):
super().__init__(name)
# Persist the latest sample.
qos = QoSProfile(
depth=1,
durability=DurabilityPolicy.TRANSIENT_LOCAL,
history=HistoryPolicy.KEEP_LAST,
reliability=ReliabilityPolicy.RELIABLE
)
self._state_publisher = self.create_publisher(
PlannerState,
"/planner/state",
qos
)
self._state_subscriber = self.create_subscription(
PlannerState,
'/planner/state',
self.state_updated,
10
)
self._state = None
def state_updated(self, msg):
self._state = msg
RenameTargetNode implementation:
class RenameTargetNode(StateNode):
def __init__(self):
super().__init__('rename_target')
self.create_service(RenameTarget, '/planner/rename_target', self.rename_target_callback)
def rename_target_callback(self, request, response):
state = self._state
if state is None:
response.success = False
return response
self.get_logger().info('Renaming {} to {}'.format(request.name, request.new_name))
i = 0
for target in state.targets:
# Name already exists
if target.name == request.new_name:
response.success = False
return response
# Save index of target in case new_name is unique
if target.name == request.name:
i = state.targets.index(target)
state.targets[i].name = request.new_name
self._state_publisher.publish(state)
response.success = True
return response
AddTargetNode implementation
class AddTargetNode(StateNode):
def __init__(self):
super().__init__('add_target')
self.create_service(AddTarget, '/planner/add_target', self.add_target_callback)
def first_available_target_name(self):
if self._state is None:
return "Target-0"
target_names = [target.name for target in self._state.targets]
idx = 0
while True:
target_name = "Target-{}".format(idx)
if target_name not in target_names:
break
idx += 1
return target_name
def create_new_target(self, pose):
target = Target()
target.name = self.first_available_target_name()
target.type = "Target"
target.comment = ""
target.selected = False
target.target = False # XXX: Misnomer
target.pose = pose
target.intensity = 100.0
target.iti = 100.0
return target
def add_target_callback(self, request, response):
self.get_logger().info('Incoming request')
target = self.create_new_target(
pose=request.target # XXX: Misnomer
)
if self._state is None:
msg = PlannerState()
msg.targets = [
target
]
else:
msg = self._state
msg.targets.append(target)
self._state_publisher.publish(msg)
response.success = True
return response
System information:
Ubuntu 20.04, kernel 5.14.0-1042-oem, x86_64
I'm running the ros nodes in one docker container created with osrf/ros:galactic-desktop.
The problem here was that I had several publishers to the same topic with DurabilityPolicy.TRANSIENT_LOCAL, which is described as follows: "the publisher becomes responsible for persisting samples for “late-joining” subscriptions." In practice this means that when a new subscriber joins, each publisher will send them their last message --> subscriber receives multiple messages.
There are several solutions for this, for example creating a master node that is subscribed to an inner state that is updated by each node, but only the master node is responsible for publishing the state "outside".
Consider a reStructuredText document with this skeleton:
Main Title
==========
text text text text text
Subsection
----------
text text text text text
.. my-import-from:: file1
.. my-import-from:: file2
The my-import-from directive is provided by a document-specific Sphinx extension, which is supposed to read the file provided as its argument, parse reST embedded in it, and inject the result as a section in the current input file. (Like autodoc, but for a different file format.) The code I have for that, right now, looks like this:
class MyImportFromDirective(Directive):
required_arguments = 1
def run(self):
src, srcline = self.state_machine.get_source_and_line()
doc_file = os.path.normpath(os.path.join(os.path.dirname(src),
self.arguments[0]))
self.state.document.settings.record_dependencies.add(doc_file)
doc_text = ViewList()
try:
doc_text = extract_doc_from_file(doc_file)
except EnvironmentError as e:
raise self.error(e.filename + ": " + e.strerror) from e
doc_section = nodes.section()
doc_section.document = self.state.document
# report line numbers within the nested parse correctly
old_reporter = self.state.memo.reporter
self.state.memo.reporter = AutodocReporter(doc_text,
self.state.memo.reporter)
nested_parse_with_titles(self.state, doc_text, doc_section)
self.state.memo.reporter = old_reporter
if len(doc_section) == 1 and isinstance(doc_section[0], nodes.section):
doc_section = doc_section[0]
# If there was no title, synthesize one from the name of the file.
if len(doc_section) == 0 or not isinstance(doc_section[0], nodes.title):
doc_title = nodes.title()
doc_title.append(make_title_text(doc_file))
doc_section.insert(0, doc_title)
return [doc_section]
This works, except that the new section is injected as a child of the current section, rather than a sibling. In other words, the example document above produces a TOC tree like this:
Main Title
Subsection
File1
File2
instead of the desired
Main Title
Subsection
File1
File2
How do I fix this? The Docutils documentation is ... inadequate, particularly regarding control of section depth. One obvious thing I have tried is returning doc_section.children instead of [doc_section]; that completely removes File1 and File2 from the TOC tree (but does make the section headers in the body of the document appear to be for the right nesting level).
I don't think it is possible to do this by returning the section from the directive (without doing something along the lines of what Florian suggested), as it will get appended to the 'current' section. You can, however, add the section via self.state.section as I do in the following (handling of options removed for brevity)
class FauxHeading(object):
"""
A heading level that is not defined by a string. We need this to work with
the mechanics of
:py:meth:`docutils.parsers.rst.states.RSTState.check_subsection`.
The important thing is that the length can vary, but it must be equal to
any other instance of FauxHeading.
"""
def __init__(self, length):
self.length = length
def __len__(self):
return self.length
def __eq__(self, other):
return isinstance(other, FauxHeading)
class ParmDirective(Directive):
required_arguments = 1
optional_arguments = 0
has_content = True
option_spec = {
'type': directives.unchanged,
'precision': directives.nonnegative_int,
'scale': directives.nonnegative_int,
'length': directives.nonnegative_int}
def run(self):
variableName = self.arguments[0]
lineno = self.state_machine.abs_line_number()
secBody = None
block_length = 0
# added for some space
lineBlock = nodes.line('', '', nodes.line_block())
# parse the body of the directive
if self.has_content and len(self.content):
secBody = nodes.container()
block_length += nested_parse_with_titles(
self.state, self.content, secBody)
# keeping track of the level seems to be required if we want to allow
# nested content. Not sure why, but fits with the pattern in
# :py:meth:`docutils.parsers.rst.states.RSTState.new_subsection`
myLevel = self.state.memo.section_level
self.state.section(
variableName,
'',
FauxHeading(2 + len(self.options) + block_length),
lineno,
[lineBlock] if secBody is None else [lineBlock, secBody])
self.state.memo.section_level = myLevel
return []
I don't know how to do it directly inside your custom directive. However, you can use a custom transform to raise the File1 and File2 nodes in the tree after parsing. For example, see the transforms in the docutils.transforms.frontmatter module.
In your Sphinx extension, use the Sphinx.add_transform method to register the custom transform.
Update: You can also directly register the transform in your directive by returning one or more instances of the docutils.nodes.pending class in your node list. Make sure to call the note_pending method of the document in that case (in your directive you can get the document via self.state_machine.document).
I'm trying to read the target file/directory of a shortcut (.lnk) file from Python. Is there a headache-free way to do it? The spec is way over my head.
I don't mind using Windows-only APIs.
My ultimate goal is to find the "(My) Videos" folder on Windows XP and Vista. On XP, by default, it's at %HOMEPATH%\My Documents\My Videos, and on Vista it's %HOMEPATH%\Videos. However, the user can relocate this folder. In the case, the %HOMEPATH%\Videos folder ceases to exists and is replaced by %HOMEPATH%\Videos.lnk which points to the new "My Videos" folder. And I want its absolute location.
Create a shortcut using Python (via WSH)
import sys
import win32com.client
shell = win32com.client.Dispatch("WScript.Shell")
shortcut = shell.CreateShortCut("t:\\test.lnk")
shortcut.Targetpath = "t:\\ftemp"
shortcut.save()
Read the Target of a Shortcut using Python (via WSH)
import sys
import win32com.client
shell = win32com.client.Dispatch("WScript.Shell")
shortcut = shell.CreateShortCut("t:\\test.lnk")
print(shortcut.Targetpath)
I know this is an older thread but I feel that there isn't much information on the method that uses the link specification as noted in the original question.
My shortcut target implementation could not use the win32com module and after a lot of searching, decided to come up with my own. Nothing else seemed to accomplish what I needed under my restrictions. Hopefully this will help other folks in this same situation.
It uses the binary structure Microsoft has provided for MS-SHLLINK.
import struct
path = 'myfile.txt.lnk'
target = ''
with open(path, 'rb') as stream:
content = stream.read()
# skip first 20 bytes (HeaderSize and LinkCLSID)
# read the LinkFlags structure (4 bytes)
lflags = struct.unpack('I', content[0x14:0x18])[0]
position = 0x18
# if the HasLinkTargetIDList bit is set then skip the stored IDList
# structure and header
if (lflags & 0x01) == 1:
position = struct.unpack('H', content[0x4C:0x4E])[0] + 0x4E
last_pos = position
position += 0x04
# get how long the file information is (LinkInfoSize)
length = struct.unpack('I', content[last_pos:position])[0]
# skip 12 bytes (LinkInfoHeaderSize, LinkInfoFlags, and VolumeIDOffset)
position += 0x0C
# go to the LocalBasePath position
lbpos = struct.unpack('I', content[position:position+0x04])[0]
position = last_pos + lbpos
# read the string at the given position of the determined length
size= (length + last_pos) - position - 0x02
temp = struct.unpack('c' * size, content[position:position+size])
target = ''.join([chr(ord(a)) for a in temp])
Alternatively, you could try using SHGetFolderPath(). The following code might work, but I'm not on a Windows machine right now so I can't test it.
import ctypes
shell32 = ctypes.windll.shell32
# allocate MAX_PATH bytes in buffer
video_folder_path = ctypes.create_string_buffer(260)
# 0xE is CSIDL_MYVIDEO
# 0 is SHGFP_TYPE_CURRENT
# If you want a Unicode path, use SHGetFolderPathW instead
if shell32.SHGetFolderPathA(None, 0xE, None, 0, video_folder_path) >= 0:
# success, video_folder_path now contains the correct path
else:
# error
Basically call the Windows API directly. Here is a good example found after Googling:
import os, sys
import pythoncom
from win32com.shell import shell, shellcon
shortcut = pythoncom.CoCreateInstance (
shell.CLSID_ShellLink,
None,
pythoncom.CLSCTX_INPROC_SERVER,
shell.IID_IShellLink
)
desktop_path = shell.SHGetFolderPath (0, shellcon.CSIDL_DESKTOP, 0, 0)
shortcut_path = os.path.join (desktop_path, "python.lnk")
persist_file = shortcut.QueryInterface (pythoncom.IID_IPersistFile)
persist_file.Load (shortcut_path)
shortcut.SetDescription ("Updated Python %s" % sys.version)
mydocs_path = shell.SHGetFolderPath (0, shellcon.CSIDL_PERSONAL, 0, 0)
shortcut.SetWorkingDirectory (mydocs_path)
persist_file.Save (shortcut_path, 0)
This is from http://timgolden.me.uk/python/win32_how_do_i/create-a-shortcut.html.
You can search for "python ishelllink" for other examples.
Also, the API reference helps too: http://msdn.microsoft.com/en-us/library/bb774950(VS.85).aspx
I also realize this question is old, but I found the answers to be most relevant to my situation.
Like Jared's answer, I also could not use the win32com module. So Jared's use of the binary structure from MS-SHLLINK got me part of the way there. I needed read shortcuts on both Windows and Linux, where the shortcuts are created on a samba share by Windows. Jared's implementation didn't quite work for me, I think only because I encountered some different variations on the shortcut format. But, it gave me the start I needed (thanks Jared).
So, here is a class named MSShortcut which expands on Jared's approach. However, the implementation is only Python3.4 and above, due to using some pathlib features added in Python3.4
#!/usr/bin/python3
# Link Format from MS: https://msdn.microsoft.com/en-us/library/dd871305.aspx
# Need to be able to read shortcut target from .lnk file on linux or windows.
# Original inspiration from: http://stackoverflow.com/questions/397125/reading-the-target-of-a-lnk-file-in-python
from pathlib import Path, PureWindowsPath
import struct, sys, warnings
if sys.hexversion < 0x03040000:
warnings.warn("'{}' module requires python3.4 version or above".format(__file__), ImportWarning)
# doc says class id =
# 00021401-0000-0000-C000-000000000046
# requiredCLSID = b'\x00\x02\x14\x01\x00\x00\x00\x00\xC0\x00\x00\x00\x00\x00\x00\x46'
# Actually Getting:
requiredCLSID = b'\x01\x14\x02\x00\x00\x00\x00\x00\xC0\x00\x00\x00\x00\x00\x00\x46' # puzzling
class ShortCutError(RuntimeError):
pass
class MSShortcut():
"""
interface to Microsoft Shortcut Objects. Purpose:
- I need to be able to get the target from a samba shared on a linux machine
- Also need to get access from a Windows machine.
- Need to support several forms of the shortcut, as they seem be created differently depending on the
creating machine.
- Included some 'flag' types in external interface to help test differences in shortcut types
Args:
scPath (str): path to shortcut
Limitations:
- There are some omitted object properties in the implementation.
Only implemented / tested enough to recover the shortcut target information. Recognized omissions:
- LinkTargetIDList
- VolumeId structure (if captured later, should be a separate class object to hold info)
- Only captured environment block from extra data
- I don't know how or when some of the shortcut information is used, only captured what I recognized,
so there may be bugs related to use of the information
- NO shortcut update support (though might be nice)
- Implementation requires python 3.4 or greater
- Tested only with Unicode data on a 64bit little endian machine, did not consider potential endian issues
Not Debugged:
- localBasePath - didn't check if parsed correctly or not.
- commonPathSuffix
- commonNetworkRelativeLink
"""
def __init__(self, scPath):
"""
Parse and keep shortcut properties on creation
"""
self.scPath = Path(scPath)
self._clsid = None
self._lnkFlags = None
self._lnkInfoFlags = None
self._localBasePath = None
self._commonPathSuffix = None
self._commonNetworkRelativeLink = None
self._name = None
self._relativePath = None
self._workingDir = None
self._commandLineArgs = None
self._iconLocation = None
self._envTarget = None
self._ParseLnkFile(self.scPath)
#property
def clsid(self):
return self._clsid
#property
def lnkFlags(self):
return self._lnkFlags
#property
def lnkInfoFlags(self):
return self._lnkInfoFlags
#property
def localBasePath(self):
return self._localBasePath
#property
def commonPathSuffix(self):
return self._commonPathSuffix
#property
def commonNetworkRelativeLink(self):
return self._commonNetworkRelativeLink
#property
def name(self):
return self._name
#property
def relativePath(self):
return self._relativePath
#property
def workingDir(self):
return self._workingDir
#property
def commandLineArgs(self):
return self._commandLineArgs
#property
def iconLocation(self):
return self._iconLocation
#property
def envTarget(self):
return self._envTarget
#property
def targetPath(self):
"""
Args:
woAnchor (bool): remove the anchor (\\server\path or drive:) from returned path.
Returns:
a libpath PureWindowsPath object for combined workingDir/relative path
or the envTarget
Raises:
ShortCutError when no target path found in Shortcut
"""
target = None
if self.workingDir:
target = PureWindowsPath(self.workingDir)
if self.relativePath:
target = target / PureWindowsPath(self.relativePath)
else: target = None
if not target and self.envTarget:
target = PureWindowsPath(self.envTarget)
if not target:
raise ShortCutError("Unable to retrieve target path from MS Shortcut: shortcut = {}"
.format(str(self.scPath)))
return target
#property
def targetPathWOAnchor(self):
tp = self.targetPath
return tp.relative_to(tp.anchor)
def _ParseLnkFile(self, lnkPath):
with lnkPath.open('rb') as f:
content = f.read()
# verify size (4 bytes)
hdrSize = struct.unpack('I', content[0x00:0x04])[0]
if hdrSize != 0x4C:
raise ShortCutError("MS Shortcut HeaderSize = {}, but required to be = {}: shortcut = {}"
.format(hdrSize, 0x4C, str(lnkPath)))
# verify LinkCLSID id (16 bytes)
self._clsid = bytes(struct.unpack('B'*16, content[0x04:0x14]))
if self._clsid != requiredCLSID:
raise ShortCutError("MS Shortcut ClassID = {}, but required to be = {}: shortcut = {}"
.format(self._clsid, requiredCLSID, str(lnkPath)))
# read the LinkFlags structure (4 bytes)
self._lnkFlags = struct.unpack('I', content[0x14:0x18])[0]
#logger.debug("lnkFlags=0x%0.8x" % self._lnkFlags)
position = 0x4C
# if HasLinkTargetIDList bit, then position to skip the stored IDList structure and header
if (self._lnkFlags & 0x01):
idListSize = struct.unpack('H', content[position:position+0x02])[0]
position += idListSize + 2
# if HasLinkInfo, then process the linkinfo structure
if (self._lnkFlags & 0x02):
(linkInfoSize, linkInfoHdrSize, self._linkInfoFlags,
volIdOffset, localBasePathOffset,
cmnNetRelativeLinkOffset, cmnPathSuffixOffset) = struct.unpack('IIIIIII', content[position:position+28])
# check for optional offsets
localBasePathOffsetUnicode = None
cmnPathSuffixOffsetUnicode = None
if linkInfoHdrSize >= 0x24:
(localBasePathOffsetUnicode, cmnPathSuffixOffsetUnicode) = struct.unpack('II', content[position+28:position+36])
#logger.debug("0x%0.8X" % linkInfoSize)
#logger.debug("0x%0.8X" % linkInfoHdrSize)
#logger.debug("0x%0.8X" % self._linkInfoFlags)
#logger.debug("0x%0.8X" % volIdOffset)
#logger.debug("0x%0.8X" % localBasePathOffset)
#logger.debug("0x%0.8X" % cmnNetRelativeLinkOffset)
#logger.debug("0x%0.8X" % cmnPathSuffixOffset)
#logger.debug("0x%0.8X" % localBasePathOffsetUnicode)
#logger.debug("0x%0.8X" % cmnPathSuffixOffsetUnicode)
# if info has a localBasePath
if (self._linkInfoFlags & 0x01):
bpPosition = position + localBasePathOffset
# not debugged - don't know if this works or not
self._localBasePath = UnpackZ('z', content[bpPosition:])[0].decode('ascii')
#logger.debug("localBasePath: {}".format(self._localBasePath))
if localBasePathOffsetUnicode:
bpPosition = position + localBasePathOffsetUnicode
self._localBasePath = UnpackUnicodeZ('z', content[bpPosition:])[0]
self._localBasePath = self._localBasePath.decode('utf-16')
#logger.debug("localBasePathUnicode: {}".format(self._localBasePath))
# get common Path Suffix
cmnSuffixPosition = position + cmnPathSuffixOffset
self._commonPathSuffix = UnpackZ('z', content[cmnSuffixPosition:])[0].decode('ascii')
#logger.debug("commonPathSuffix: {}".format(self._commonPathSuffix))
if cmnPathSuffixOffsetUnicode:
cmnSuffixPosition = position + cmnPathSuffixOffsetUnicode
self._commonPathSuffix = UnpackUnicodeZ('z', content[cmnSuffixPosition:])[0]
self._commonPathSuffix = self._commonPathSuffix.decode('utf-16')
#logger.debug("commonPathSuffix: {}".format(self._commonPathSuffix))
# check for CommonNetworkRelativeLink
if (self._linkInfoFlags & 0x02):
relPosition = position + cmnNetRelativeLinkOffset
self._commonNetworkRelativeLink = CommonNetworkRelativeLink(content, relPosition)
position += linkInfoSize
# If HasName
if (self._lnkFlags & 0x04):
(position, self._name) = self.readStringObj(content, position)
#logger.debug("name: {}".format(self._name))
# get relative path string
if (self._lnkFlags & 0x08):
(position, self._relativePath) = self.readStringObj(content, position)
#logger.debug("relPath='{}'".format(self._relativePath))
# get working dir string
if (self._lnkFlags & 0x10):
(position, self._workingDir) = self.readStringObj(content, position)
#logger.debug("workingDir='{}'".format(self._workingDir))
# get command line arguments
if (self._lnkFlags & 0x20):
(position, self._commandLineArgs) = self.readStringObj(content, position)
#logger.debug("commandLineArgs='{}'".format(self._commandLineArgs))
# get icon location
if (self._lnkFlags & 0x40):
(position, self._iconLocation) = self.readStringObj(content, position)
#logger.debug("iconLocation='{}'".format(self._iconLocation))
# look for environment properties
if (self._lnkFlags & 0x200):
while True:
size = struct.unpack('I', content[position:position+4])[0]
#logger.debug("blksize=%d" % size)
if size==0: break
signature = struct.unpack('I', content[position+4:position+8])[0]
#logger.debug("signature=0x%0.8x" % signature)
# EnvironmentVariableDataBlock
if signature == 0xA0000001:
if (self._lnkFlags & 0x80): # unicode
self._envTarget = UnpackUnicodeZ('z', content[position+268:])[0]
self._envTarget = self._envTarget.decode('utf-16')
else:
self._envTarget = UnpackZ('z', content[position+8:])[0].decode('ascii')
#logger.debug("envTarget='{}'".format(self._envTarget))
position += size
def readStringObj(self, scContent, position):
"""
returns:
tuple: (newPosition, string)
"""
strg = ''
size = struct.unpack('H', scContent[position:position+2])[0]
#logger.debug("workingDirSize={}".format(size))
if (self._lnkFlags & 0x80): # unicode
size *= 2
strg = struct.unpack(str(size)+'s', scContent[position+2:position+2+size])[0]
strg = strg.decode('utf-16')
else:
strg = struct.unpack(str(size)+'s', scContent[position+2:position+2+size])[0].decode('ascii')
#logger.debug("strg='{}'".format(strg))
position += size + 2 # 2 bytes to account for CountCharacters field
return (position, strg)
class CommonNetworkRelativeLink():
def __init__(self, scContent, linkContentPos):
self._networkProviderType = None
self._deviceName = None
self._netName = None
(linkSize, flags, netNameOffset,
devNameOffset, self._networkProviderType) = struct.unpack('IIIII', scContent[linkContentPos:linkContentPos+20])
#logger.debug("netnameOffset = {}".format(netNameOffset))
if netNameOffset > 0x014:
(netNameOffsetUnicode, devNameOffsetUnicode) = struct.unpack('II', scContent[linkContentPos+20:linkContentPos+28])
#logger.debug("netnameOffsetUnicode = {}".format(netNameOffsetUnicode))
self._netName = UnpackUnicodeZ('z', scContent[linkContentPos+netNameOffsetUnicode:])[0]
self._netName = self._netName.decode('utf-16')
self._deviceName = UnpackUnicodeZ('z', scContent[linkContentPos+devNameOffsetUnicode:])[0]
self._deviceName = self._deviceName.decode('utf-16')
else:
self._netName = UnpackZ('z', scContent[linkContentPos+netNameOffset:])[0].decode('ascii')
self._deviceName = UnpackZ('z', scContent[linkContentPos+devNameOffset:])[0].decode('ascii')
#property
def deviceName(self):
return self._deviceName
#property
def netName(self):
return self._netName
#property
def networkProviderType(self):
return self._networkProviderType
def UnpackZ (fmt, buf) :
"""
Unpack Null Terminated String
"""
#logger.debug(bytes(buf))
while True :
pos = fmt.find ('z')
if pos < 0 :
break
z_start = struct.calcsize (fmt[:pos])
z_len = buf[z_start:].find(b'\0')
#logger.debug(z_len)
fmt = '%s%dsx%s' % (fmt[:pos], z_len, fmt[pos+1:])
#logger.debug("fmt='{}', len={}".format(fmt, z_len))
fmtlen = struct.calcsize(fmt)
return struct.unpack (fmt, buf[0:fmtlen])
def UnpackUnicodeZ (fmt, buf) :
"""
Unpack Null Terminated String
"""
#logger.debug(bytes(buf))
while True :
pos = fmt.find ('z')
if pos < 0 :
break
z_start = struct.calcsize (fmt[:pos])
# look for null bytes by pairs
z_len = 0
for i in range(z_start,len(buf),2):
if buf[i:i+2] == b'\0\0':
z_len = i-z_start
break
fmt = '%s%dsxx%s' % (fmt[:pos], z_len, fmt[pos+1:])
# logger.debug("fmt='{}', len={}".format(fmt, z_len))
fmtlen = struct.calcsize(fmt)
return struct.unpack (fmt, buf[0:fmtlen])
I hope this helps others as well.
Thanks
I didn't really like any of the answers available because I didn't want to keep importing more and more libraries and the 'shell' option was spotty on my test machines. I opted for reading the ".lnk" in and then using a regular expression to read out the path. For my purposes, I am looking for pdf files that were recently opened and then reading the content of those files:
# Example file path to the shortcut
shortcut = "shortcutFileName.lnk"
# Open the lnk file using the ISO-8859-1 encoder to avoid errors for special characters
lnkFile = open(shortcut, 'r', encoding = "ISO-8859-1")
# Use a regular expression to parse out the pdf file on C:\
filePath = re.findall("C:.*?pdf", lnkFile.read(), flags=re.DOTALL)
# Close File
lnkFile.close()
# Read the pdf at the lnk Target
pdfFile = open(tmpFilePath[0], 'rb')
Comments:
Obviously this works for pdf but needs to specify other file extensions accordingly.
It's easy as opening ".exe" file. Here also, we are going to use the os module for this. You just have to create a shortcut .lnk and store it in any folder of your choice. Then, in any Python file, first import the os module (already installed, just import). Then, use a variable, say path, and assign it a string value containing the location of your .lnk file. Just create a shortcut of your desired application. At last, we will use os.startfile()
to open our shortcut.
Points to remember:
The location should be within double inverted commas.
Most important, open Properties. Then, under that, open "Details". There, you can get the exact name of your shortcut. Please write that name with ".lnk" at last.
Now, you have completed the procedure. I hope it helps you. For additional assistance, I am leaving my code for this at the bottom.
import os
path = "C:\\Users\\hello\\OneDrive\\Desktop\\Shortcuts\\OneNote for Windows 10.lnk"
os.startfile(path)
In my code, I used path as variable and I had created a shortcut for OneNote. In path, I defined the location of OneNote's shortcut. So when I use os.startfile(path), the os module is going to open my shortcut file defined in variable path.
this job is possible without any modules, doing this will return a b string having the destination of the shortcut file. Basically what you do is you open the file in read binary mode (rb mode). This is the code to accomplish this task:
with open('programs.lnk - Copy','rb') as f:
destination=f.read()
i am currently using python 3.9.2, in case you face problems with this, just tell me and i will try to fix it.
A more stable solution in python, using powershell to read the target path from the .lnk file.
using only standard libraries avoids introducing extra dependencies such as win32com
this approach works with the .lnks that failed with jared's answer, more details
we avoid directly reading the file, which felt hacky, and sometimes failed
import subprocess
def get_target(link_path) -> (str, str):
"""
Get the target & args of a Windows shortcut (.lnk)
:param link_path: The Path or string-path to the shortcut, e.g. "C:\\Users\\Public\\Desktop\\My Shortcut.lnk"
:return: A tuple of the target and arguments, e.g. ("C:\\Program Files\\My Program.exe", "--my-arg")
"""
# get_target implementation by hannes, https://gist.github.com/Winand/997ed38269e899eb561991a0c663fa49
ps_command = \
"$WSShell = New-Object -ComObject Wscript.Shell;" \
"$Shortcut = $WSShell.CreateShortcut(\"" + str(link_path) + "\"); " \
"Write-Host $Shortcut.TargetPath ';' $shortcut.Arguments "
output = subprocess.run(["powershell.exe", ps_command], capture_output=True)
raw = output.stdout.decode('utf-8')
launch_path, args = [x.strip() for x in raw.split(';', 1)]
return launch_path, args
# to test
shortcut_file = r"C:\Users\REPLACE_WITH_USERNAME\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Accessibility\Narrator.lnk"
a, args = get_target(shortcut_file)
print(a) # C:\WINDOWS\system32\narrator.exe
(you can remove -> typehinting to get it to work in older python versions)
I did notice this is slow when running on lots of shortcuts. You could use jareds method, check if the result is None, and if so, run this code to get the target path.
The nice approach with direct regex-based parsing (proposed in the answer) didn't work reliable for all shortcuts in my case. Some of them have only relative path like ..\\..\\..\\..\\..\\..\\Program Files\\ImageGlass\\ImageGlass.exe (produced by msi-installer), and it is stored with wide chars, which are tricky to handle in Python.
So I've discovered a Python module LnkParse3, which is easy to use and meets my needs.
Here is a sample script to show target of a lnk-file passed as first argument:
import LnkParse3
import sys
with open(sys.argv[1], 'rb') as indata:
lnk = LnkParse3.lnk_file(indata)
print(lnk.lnk_command)
I arrived at this thread looking for a way to parse a ".lnk" file and get the target file name.
I found another very simple solution:
pip install comtypes
Then
from comtypes.client import CreateObject
from comtypes.persist import IPersistFile
from comtypes.shelllink import ShellLink
# MAKE SURE THIS VAT CONTAINS A STRING AND NOT AN OBJECT OF 'PATH'
# I spent too much time figuring out the problem with .load(..) function ahead
pathStr="c:\folder\yourlink.lnk"
s = CreateObject(ShellLink)
p = s.QueryInterface(IPersistFile)
p.Load(pathStr, False)
print(s.GetPath())
print(s.GetArguments())
print(s.GetWorkingDirectory())
print(s.GetIconLocation())
try:
# the GetDescription create exception in some of the links
print(s.GetDescription())
except Exception as e:
print(e)
print(s.Hotkey)
print(s.ShowCmd)
Based on this great answer...
https://stackoverflow.com/a/43856809/2992810