Can somebody please guide me a way to clean all existing content in a file before writing new info to it in Ruby? I'm writing the contents of this file with the code below:
logfile = File.new(filepath, "w")
logfile.write("my content")
However, I want all existing content in this "logfile" to be deleted before I write new info to it. How can I do this?
When opening a file for writing, i.e. using the "w" option, all previous contents of the file will be removed so you don't have to do anything explicitly to achieve that effect.
Related
I have a tar.gz file saved on disk and I want to leave it packed there, but I need to open one file within the archive, read from it and save some information somewhere.
File structure:
base_folder
file_i_need.txt
other_folder
other_file
code (it is not much - I tried 10mio different ways and this is what is left)
def self.open_file(file)
uncompressed_file = Gem::Package::TarReader.new(Zlib::GzipReader.open(file))
uncompressed_file.rewind
end
When I run it in a console I get
<Gem::Package::TarReader:0x007fbaac178090>
and I can run commands on the entries. I just haven't figured out how to open an entry and read from it without saving it unpacked to disk. I mainly need the string from the text file.
Any help appreciated. I might just be missing something...
TarReader is Enumerable, returning Entry.
That said, to retrieve the text content from the file by it’s name one might
uncompressed = Gem::Package::TarReader.new(Zlib::GzipReader.open(file))
text = uncompressed.detect do |f|
f.fullname == 'base_folder/file_i_need.txt'
end.read
#⇒ Hello, I’m content of the text file, located inside gzipped tar
Hope it helps.
I have a couple of files that i'd like to turn into Tempfile objects.
Is there a way to do something like: Tempfile.new(path)?
The reason i'm asking is that I'm trying to run an ImageMagick command that creates multiple files from a single Tempfile. Unfortunatly the newly created files do not get garbage collected...
Thanks!
Just thought of something. Instead of dumping the new file into a Tempfile, just overwrite it.
tempfile = Tempfile.new('foo')
tempfile.close
FileUtils.mv path, tempfile.path
tempfile.open
I'm banging through Zed A. Shaw's learn code the hard way (Ruby) on compilr and am stuck on exercise 16.
filename = ARGV.first
target = File.open(filename, 'w')
target.truncate(target.size)
target.close()
In the console, I type
run sample.txt
This should wipe the sample.txt file, but it doesn't.
The file, sample.txt is in the same folder as the Start file.
Any clues?
Ok it's not the Ruby issue (as I expected) it's to do with how Compilr works. By running the code without having first created a sample.txt file, Compilr created the file for me by default in the content folder. So putting the uh... writable files... into the contents folder enables Compilr to write to them. Putting them all in the same folder (the script and the files) makes it not work.
I am using twitter ruby gem to fetch twitter search result. The example code from Github extracts the information from search result.I am wondering how to save the search result, which is JSON i think, to a separate JSON file.
Here is part of the example code:
results = #search.perform("$aaa", 1000)
aFile = File.new("data.txt", "w")
results.map do |status|
myStr="#{status.from_user}: #{status.text} #{status.created_at}"
aFile.write(myStr)
aFile.write("\n")
end
Is there any way to save all the search result to a separate JSON file instead of writing strings to a file?
Thanks in advance.
If you want to save to a file all you need to do is open the file, write it it, then close it:
File.open("myFileName.txt", "a") do |mFile|
mFile.syswrite("Your content here")
mFile.close
end
When you use open you will create the file if it doesn't exist.
One thing to be aware of is that there are different ways to open file, of which will determine where the program writes to. The "a" indicates that it will append everything you write to the file, to the end of the current content.
Here is some of the options:
r Read-only mode. The file pointer is placed at the beginning of the file. This is the default mode.
r+ Read-write mode. The file pointer will be at the beginning of the file.
w Write-only mode. Overwrites the file if the file exists. If the file does not exist, creates a new file for writing.
w+ Read-write mode. Overwrites the existing file if the file exists. If the file does not exist, creates a new file for reading and writing.
a Write-only mode. The file pointer is at the end of the file if the file exists. That is, the file is in the append mode. If the file does not exist, it creates a new file for writing.
a+ Read and write mode. The file pointer is at the end of the file if the file exists. The file opens in the append mode. If the file does not exist, it creates a new file for reading and writing.
So in your case, you would want to pull out the data you want to save, then write it to a file as I have shown. You can also specify file paths by doing:
File.open("/the/path/to/yourfile/myFileName.txt", "a") do |mFile|
mFile.syswrite("Your content here")
mFile.close
end
Another thing to be aware of is that open does not create directories, so you will either need to create directories yourself, or you can do it with your program. Here is a link that is helpful for file input/output:
http://www.tutorialspoint.com/ruby/ruby_input_output.htm
Hi I'm trying to read a pdf in Ruby, first of all I want to convert it into a txt. path is the path to the PDF, The point is that I get a .txt file empty, and as someone told me is a pdftotext problem, but I don't know how to fix it.
spec = path.sub(/\.pdf$/, '')
`pdftotext #{spec}.pdf`
file = File.new("#{spec}.txt", "w+")
text = []
file.readlines.each do |l|
if l.length > 0
text << l
Rails.logger.info l
end
end
file.close
What's wrong with my code? Thanks!
It's not possible to extract text from every PDF. Some PDF files use a font encoding that makes it impossible to extract text with simple tools such as pdftotext (and some PDF files are even completely immune to direct text extraction with any tool known to me -- in these cases you'll have to apply OCR first to have a chance to extract text...).
So if you test your code with the same "weird" PDF file all the time, it may well happen that you're getting frustrated over your code while in reality the fault lies with the PDF.
First make sure that the commandline usage of pdftotxt works well with a given PDF, then test (and develop further) your code with that PDF.
The problem is you are opening the file in write ("w") mode, whuch truncates the file. You can see a table of file modes and what they mean at http://ruby-doc.org/core-1.9.3/IO.html.
Try something like this, it uses a pdftotext option to send the text to stdout to avoid creating a temporary file and uses blocks for more idiomatic ruby.
text = `pdftotext #{path} -`
text.split.select { |line|
line.length > 0
}.each { |line|
Rails.logger.info(line)
}
You would need to open the txt file with write permission.
file = File.new("#{spec}.txt", "w")
You could consult How to create a file in Ruby
Update: your code is not complete and looks buggy.
Cant say what is path
Looks like you are trying to read the text file to which you intend to write file.readlines.each
spell check length you have it l.lenght
You may want to paste the actual code.
Check this gist https://gist.github.com/4160587
As mentioned, your code is not working because you are reading and writing to the same file.
Example
Ruby code file_write.rb to do the file write operation
pdf_file = File.open("in.txt")
output_file = File.open("out.txt", "w") # file to which you want to write
#iterate over input file and write the content to output file
pdf_file.readlines.each do |l|
output_file.puts(l)
end
output_file.close
pdf_file.close
Sample txt file in.txt
Some text in file
Another line of text
1. Line 1
2. Not really line 2
Once your run file_write.rb you should see new file called out.txt with same content as in.txt You could change the content of input file if you want. In your case you would use pdf reader to get the content and write it to the text file. Basically first line of the code will change.