I've two methods. One is for image comparison and one is for file reading. what i do is I call a process that compares images between two folders and creates a logfile. Now the second method reads that logfile and parse the data.
But when i call the second method, it says, file not exist, this is because the exe take a little time to make the logfile.
I have used Thread.Sleep() but it still don't work, neither i can use that file.exist method as if i use it and if file does not exist then it will skip that method/file which i don't want.
You can use Process.WaitForExit to wait until your first process is finished, then you know when your log file will be complete/exist when calling your second method.
Related
As I review these file system flags, I'm I correct in concluding that there is no flag you can pass to fs.promises.writeFile that will automatically create all missing directories leading up to a filename? If not, which flag does this?
I don't like solutions that check for the existence of the folders first before attempting writeFile, because after the folders are created that check happens every time you write to a file in that folder.
In my program, after the folders are created once, it should always be there, so it seems more efficient to only create the folders if there is an exception. However, I'm hoping there is a flag that avoids all this micro-management.
If a flag for auto-creating the folders doesn't exist for writeFile, then I'd like to attempt writeFile first, and then (only if there is an exception) create the folders recursively.
fs.promises.writeFile() does not automatically create the directory structure for you. That must exist first.
If you want to automatically create the path because you received an error indicative of a path problem, you can use fs.promises.mkdir() and pass the recursive flag.
And you could, of course, create your own wrapper function that calls fs.promises.writeFile() and if it gets whatever error you get when the path doesn't exist (you'd have to test to see exactly what that error is), then call fs.promises.mkdir() and then repeat the fs.promises.writeFile(). It could all be wrapped in your own utility function.
I have a rather peculiar file format to work with:
Every line begins with the checksum of its content, followed by a new-line-character.
It looks like this:
[CHECKSUM OF LINE_1][LINE_1]\n
[CHECKSUM OF LINE_2][LINE_2]\n
[CHECKSUM OF LINE_3][LINE_3]\n
...
My goal: To allow any application to work with these files like they would work with any other text file - unaware of the additional checksums at the beginning of each line.
Since I work on a linux machine with debian wheezy (kernel 3.18.26) I want to use the LD_PRELOAD-mechanism to override the relevant file functions.
I have seen something like this with zlibc on https://zlibc.linux.lu/index.html - with an explanation of how it works ( https://zlibc.linux.lu/zlibc.html#SEC8 ).
But I dont get it. They only replace the file-opening functions. No read. No write. no fseek. Nothing. So how does it work?
Or - which functions would I have to intercept to handle every read or write operation on this file and handle them accordingly?
I didn't exactly check how it works but the reason seems to be quite simple.
Possible implementation:
zlibc open:
uncompress file you wanted to open to some temporary file
open this temporary file instead of yours
zlibc close:
Compress temporary file
Override original file
In this case you don't need to override read/write/etc because you can use original ones.
In your case you have two possible solutions:
open, that make a copy of your file with striped checksums. close that calculates checksums and override original file
read and write that are able to skip/calculate checksums.
Ad 2.
From What is the difference between read() and fread()?:
fread() is part of the C library, and provides buffered reads. It is
usually implemented by calling read() in order to fill its buffer
In this case I believe that overriding open and close will be less error prone because you can safely reuse original read, write, fread, fseek etc.
My goal is to run a bash script automatically whenever any new file is added to a particular directory or any subdirectory of that particular directory.
Detail Scenario:
I am creating an automated process for file submission from teachers to students and vice versa. Sender will upload file and it will be stored inside the Uploads directory in the LAMP server in the format, ex. "name_course-name_filename.pdf". I want some method so that when any file stored inside the Uploads folder, the same time a script will be called and send that file to the list of receives.
From the database I can find the list of receiver for that particular course and student.
The only concern of mine is, how to call a script automatically and make it work on individual file whenever the content of the directory changes. Cron will do in intervals but not a real time work.
Linux provides a nice mechanism for that purpose which is called inotify. inotify is mostly available as a C API. But there have been developed shell utilities as well. You should use inotifywait from inotifytools (pkg name in debian) for this. Here comes a basic example:
#!/bin/bash
directory="/tmp" # or whatever you are interested in
inotifywait -m -e create "$directory" |
while read folder eventlist eventfile
do
echo "the following events happened in folder $folder:"
echo "$eventlist $eventfile"
done
Update:
If the problem goes complicated, for example you'll have to monitor recursive, dynamic directory structures, you should have a look at incron It's a cron like daemon which executes scripts on certain events. But the events are file system events rather than timer events.
There is another option to 'inotifywait':
-d --daemon
Same as --monitor, except run in the background logging events to a file
that must be specified by --outfile. Implies --syslog.
For completeness:
-m --monitor
Instead of exiting after receiving a single event, execute indefinitely.
The default behaviour is to exit after the first event occurs.
Within the do-done block of your 'while' statement, you might parse each event report for interesting details then use 'case-esac' to take action based on each event that you care about.
For something that you plan to rely on for your operations, you might also consider replacing the hard-coded '$directory' with some sort of configuration file. Such a file might include the path and filename, the interesting events for that path and file, and a script to run when those events happened.
The script might take the list of events as parameters and then 'case-esac' again.
Just one man's ramblins,
~~~ 8d;-Dan
I'll explain the task requested from me:
I have two containers in Azure, one called "data" and one called "script". In the "data" container there's a txt file with data, and in the "script" container there's a script file.
Now, I need programatically (with WorkerRole) to execute the script file, with the content of the data file as parameters (Example: a script file that accepts a string 's' and returns to the screen "Hello, 's'", when 's' in the string given, and in the data file there's a string), and save the result of the run into another file which needs to be saved in another container called "result".
How do I do all these? I've already uploaded the files and created the blobs programatically, but I can't seem to understand how to execute the file of how to save its result to another file?
Can I please have some help?
Thanks in advance
Here are the steps in pseudo code:
Retrieve the script from the blob(using DownloadToStream())
Compile the script(I will leave this to you as I have no idea what
format your script is)
Load parameters from blob(same as step 1)
Execute script with those parameters.
If your script's can be written as lambda expressions then this becomes a lot easier as you can turn them into Action's
Edit based on your questiions:
DownloadText() is no longer included in Azure Storage 2.0, you only have access to DownloadToStream(). Even if you are using an older version(say 1.7) I would recommend using DownloadToStream() in the event you ever upgrade in the future. This will prevent having to refactor your code.
In terms of executing your script, depending on what type of script it is(if it is c# code you can use this example: Is it possible to dynamically compile and execute C# code fragments?. If you need to execute a different type of script you would need to run it using Process.Start and you can look at this example: http://www.dotnetperls.com/process-start
I do not have much experience with point number 2 but those are the processes I have heard and seen used.
Just like the title says...
Example: I have a file called copy.py. That file wants a path to a file/folder which it will move to another directory and will then return "done" if it successfully moved the file. For some reason I have to run my copy.py file from another python program (it's not given that both files are in the same directory) and wait for copy.py to finish its actions. When it is finished, it should tell me "done" or, let's say, "error", so I know if it actually was successful or not.
Please answer in a way a python beginner can understand...
Often, you can just import the module and call its functionality, but if it's a stand-alone program that expects command-line arguments, etc., then you may want to separate the command-line handling from the functional part of the code, so that you can import and call it as I suggested at the beginning.
Failing that, just treat it like another program:
with os.popen('python copy.py {0} {1}'.format(src, dst)) as copy:
output = copy.readlines()
if 'error' in output:
# Oops...