I am trying add an extra channel on AcqKnowledge which has the time passed during the experiment saved as milliseconds. I need that specific channel for later analyses when I export the file into text. Otherwise the time information is lost when opening the txt file. Can anyone help? Using AcqKnowledge 5.02 with MP160 Biopac Systems. Thanks!
Related
I am part of tractor pulling team and we have Bechoff CX8190 based PLC for data logging. System works most of the time but every now and then saving sensor values (every 10ms is collected) to CSV fails (mostly in middle of csv row). Guy who build the code is new with the TwinCAT and does not know how to find what causes that. Any Ideas where to look reason for this.
Writing to a file is always a asynchron action in TwinCAT. That is to say this is no realtime action and it is not safe that the writing process is done within the task cycletime of 10ms. Therefore these functionblocks always have a BUSY-output which has to be evaluated and the functionblock has to be called successivly until the BUSY-output returns to FALSE. Only then a new write command can be executed.
I normally tackle this task with a two-side-buffer algorithm. Lets say the buffer-array has 2x100 entries. So fill up the first 100 entries with sample values. Then write them all together with one command to the file. When its done, clean the buffer. In the meanwhile the other half of the buffer can be filled with sample values. If second side is full, write them all together to the file ... and so on. So you have more time for the filesystem access (in the example above 100x10ms=1s) as the 10ms task cycletime.
But this is just a suggestion out of my experience. I agree with the others, some code could really help.
I'm writing a program which needs to look at a very large number of files, some of which are very large in size. I'd like to visit a file only once, unless it changes. If it changes I need to revisit it again.
The way I know of to do this is with datestamps. One can look at the modified date to see if it is newer than the last time you looked at the file. Obviously those can be changed programmatically, so I'm wondering if there is a way to determine if a file has changed other than that. (I'm thinking along the lines of a UUID for the file which is changed every time it is modified or an epoch counter, but I'm open to more exotic solutions)
You can monitor changes for these files, assuming you continue to run the whole time. Check the FindFirstChangeNotification API. You can take a look at this project as an example. Sysinternals also has a similar tool, I believe it's implemented in a similar way.
I was trying to build a system (NodeJS + Express 4) that reads a user uploaded text file, process it, and feed it back to the user. I was trying to use ajax upload, and multer as the parser for multi-part data. The whole workflow is supposedly to be like this:
User chooses a local file, and clicks the upload button.
Server received file, and read it.
Server do some processing with the data
Send results back
Every part of the link works except the server read part - sometimes the file is not read fully even though the server signals that the file upload was completed (I have tried multiple libraries, like multer, busboy, formidable that triggers the file upload complete event). I have done various experiments, and here's what I find (with 1000 lines of file):
the fs.readFile sometimes ends prematurely. The result file can be anywhere between 100 - 1000 lines.
missing part is almost always the last small piece, feels like the pipe was not fully flushed yet. I have tried file size between 1000 lines to 200,000 lines, and it's always missing the last few hundred lines.
using streaming almost solved the issue - like createReadStream, or byline, line-by-line, but sometimes the result can be 'undefined' or missing the last few lines, but a lot less frequent.
trigger the read twice, and the second time is almost guaranteed to read the full 1000 lines.
Is there anyway to force NodeJS to 'flush' the uploaded file? Somehow I feel the upload complete event was triggered (regardless of library, and everyone is dependent on FileSystem I guess) before the last piece of file was flushed in the stream. Or maybe there are some other issues - reading a static files always give the correct results. I could use the http POST forms but I'd like to use ajax to improve user experience.
Any thoughts?
I am running some kismet captures, and I need to continuously parse the outputted PCAP files, so in order to do this I need Kismet to save the file, and start a new one periodically (I use inotify-tools to detect newly created files).
But the problem is I do not find a way for kismet to do it. In man pages i found that -m option allows to limit the file size by packet size, so I ran it like this:
sudo kismet -c wlan0 -m 10
But that did not create multiple files, it carried on just putting all traffic to one file.
Any other ways to somehow make kismet break output to different files? I don't really care about what criteria is used (time, packet count, file size.. I'll take anything)
Thanks!
I think that you can modify it in the kismet.conf file.
There is an option that says
writeinterval=300
It means that every 300 seconds the pcap file will be saved. It will make a new file every 300 seconds.If you want a shorter time you can change it.
Hope it helps
I got an application which is polling on a folder continuously. Once any file is ftp to the folder, the application has to move this file to some other folder for processing.
Here, we don't have any option to verify whether ftp is complete or not.
One command "lsof" is suggested in the technical forums. It got a file description column which gives the file status.
Since, this is a free bsd command and not present in old versions of linux, I want to clarify the usage of this command.
Can you guys tell us your experience in file verification and is there any other alternative solution available?
Also, is there any risk in using this utility?
Appreciate your help in advance.
Thanks,
Mathew Liju
We've done this before in a number of different ways.
Method one:
If you can control the process sending the files, have it send the file itself followed by a sentinel file. For example, send the real file "contracts.doc" followed by a one-byte "contracts.doc.sentinel".
Then have your listener process watch out for the sentinel files. When one of them is created, you should process the equivalent data file, then delete both.
Any data file that's more than a day old and doesn't have a corresponding sentinel file, get rid of it - it was a failed transmission.
Method two:
Keep an eye on the files themselves (specifically the last modification date/time). Only process files whose modification time is more than N minutes in the past. That increases the latency of processing the files but you can usually be certain that, if a file hasn't been written to in five minutes (for example), it's done.
Conclusion:
Both those methods have been used by us successfully in the past. I prefer the first but we had to use the second one once when we were not allowed to change the process sending the files.
The advantage of the first one is that you know the file is ready when the sentinel file appears. With both lsof (I'm assuming you're treating files that aren't open by any process as ready for processing) and the timestamps, it's possible that the FTP crashed in the middle and you may be processing half a file.
There are normally three approaches to this sort of problem.
providing a signal file so that when your file is transferred, an additional file is sent to mark that transfer is complete
add an entry to a log file within that directory to indicate a transfer is complete (this really only works if you have a single peer updating the directory, to avoid concurrency issues)
parsing the file to determine completeness. e.g. does the file start with a length field, or is it obviously incomplete ? e.g. parsing an incomplete XML file will result in a parse error due to the lack of an end element. Depending on your file's size and format, this can be trivial, or can be very time-consuming.
lsof would possibly be an option, although you've identified your Linux portability issue. If you use this, note the -F option, which formats the output suitable for processing by other programs, rather than being human-readable.
EDIT: Pax identified a fourth (!) method I'd forgotten - using the fact that the timestamp of the file hasn't updated in some time.
There is a fifth method. You can also check if the FTP Session is still active. This will work if every peer has it's own ftp user account. As long as the user is not logged off from FTP, assume the files are not complete.