I'm not very familiar with file handling in ruby. A problem I've come accross is that reading and writing a binary file doesn't produce exactly the same file.
clone = Tempfile.new(tempfile.original_filename)
FileUtils.copy_stream(tempfile, clone)
clone.flush
From the image below it is clear that it is not an exact file copy, when I try to open the newly created file in an image viewer it reports that the file is corrupt. I have tried copying the file in different ways such as clone.write(tempfile.read), etc. without success.
*The file viewer also indicates the original is ANSI Dos/Windows and the clone is ANSI Macintosh. The file size also differs by about 200 bytes.
What I'm trying to accomplish is actually simply using a Tempfile twice. A file is uploaded via rails and given to me as a Tempfile. I want to submit it to two different restful services and RestClient.post closes the file automatically. Another option would be to submit some sort of in memory stream clone to RestClient so that it can not close my file. If I submit File.open(tempfile.path) to RestClient it produces the same broken file, this indicates that the reading is the problem and not the writing. If I submit the original Tempfile object to RestClient it works perfectly but then it is closed and deleted and I cannot send it again.
Please help!
Regards,
Pierre
It would be much more helpful to see a hex view of these files instead of a text editor's intepretation. My guess is that at least one of the files is not opened in binary mode. In Ruby 1.9, try
open(filename, 'rb')
open(filename, 'wb')
Tempfile.new(filename, :binmode => true)
for opening a file for reading / writing and to create a binary temporary file, respectively.
Related
I have some txt files that store some important data for my app. Due to its nature I want them to be in external text files. Currently i plan on reading them using a streamreader that reads the txt line by line. However, i don't know where to put my txt files, so i can access them in my streamreader which requires their path. Ive seen examples of using NSBundle.mainBundlepathforResource. However, I'm not really sure what a Bundle is or how to place my files there in the first place.
You can use NSBundle. Here's another answer that shows how to create and use bundles: https://stackoverflow.com/a/23884501/1228075
I hava an application that reads a file from a ZIP archive and saves it to file on file system. After writing it to file system I start start immediately to read this file with a SAX2 reader. On bigger files (300+ MB) it sometimes occures, that SAX2 stops parsing because of an unclosed tag. But when I check the file (or even try to read it again later) it works, so the file it self it OK.
FZipKit.ExtractToStream(LFileName, LStream);
LStream.SaveToFile(OutputFilename);
SAX2.processUrl(OutputFilename);
My assumption is, that the file was not yet fully written to file system when I started the parsing process.
Is there a way to ensure, that the file was written or the steam has been flushed to file system?
thx
I'm going to first of all assume that the XML parser operates correctly. If it is incapable of reading files, well the solution is obvious.
Which leads us to look at how the file is created. When you call SaveToFile, the file is opened, written, closed and buffers are flushed. In a plain vanilla system, your XML parser will see the entire content of the file. The only conclusion is that something is interfering. The most like suspect is your virus scanner. Many scanners, even the most respected ones, cannot properly handle a file being closed and then immediately re-opened.
The bottom line is that your code is fine and the problem almost certainly lies with your local environment.
I'm trying to create PDFs that can be stored on an external server.
I do this:
File.new("temp.pdf", "w").close
File.open("temp.pdf", "wb") do |f|
f.write(bytes)
end
File.open("temp.pdf", "r") do |f|
# upload `f` to server
end
File.delete("temp.pdf")
then upload them to the server.
On my local machine this works fine, but, I recently tried running on another machine, and I got a permissions error in the log.
Is there a way to:
Write bytes to a file.
Never touch the hard disk.
Why don't you just upload the bytes to the server?
You may have to go a little lower-level than normal, but check for instance the UploadIO class of the multipart-post gem.
I realize I have to write to file and delete the file since UploadIO takes in an open file
So I created an new file, wrote the content to it, passed it in as a File.open to UploadIO, and then deleted the file after I send it.
I am using the rails gem called roo to read and parse uploaded Excel and CSV files.
I understand that in roo, the way it reads an Excel file is Excel.new("myfilename"). I am facing issue because I have to read the file uploaded with form helper (upload helper), temp file. I am saving the temp file before reading it with roo/Excel.
Though I am uplaoding good excel files, I am getting
the file is not an Excel/xlsx
error.
Is there a way to directly read from Uploaded IO?
Can you guys tell me what am I doing wrong here?
Thanks!
If you are developing on a Windows box, when you open files, you have to add a 'b' (binary) to the file mode, i.e:
File.open("spreadsheet.xls","rb")
for read only, binary.
Not sure if that's your problem, but I faced a similar problem and that was the solution.
good luck
I am not familiar with roo, but I have used http://rubygems.org/gems/parseexcel
workbook = Spreadsheet::ParseExcel.parse("#{Dir.getwd}/public/excel/foo.xls")
I have a upload text file field, and with it I plan to save the file somewhere and then store the location of the file in a database. However, I want to make sure the file they uploaded is a .txt file, and not, say, an image file. I imagine this happens in the validation step. How does one validate such a thing? Also, how do you get the filename of the uploaded file? I could always just check if it said '.txt' but for future reference knowing how to validate without just the filename would be helpful.
Trying to validate the contents of a file based on the filename extension is opening the door for major hackerdom. It's trivial to change the extension and upload the file.
If you are on a Mac/Linux/Unix-based system the OS "file" command is the standard because it looks inside the file for key bytes that flag file types. http://en.wikipedia.org/wiki/File_(Unix) I'm not sure what's available for Windows, but this might help: Determine file type in Ruby
One way of doing it, the simple way really, would be to pass the file through an image loader, preferably one that handles multiple common formats, and see if it throws an error.
The other way is to manually check the file header for common image format headers. For example, .bmp files start with BM. Other formats have their own specific markings you can use.