Hi in my java file i have a buffered reader, that is reading through a comma seperated file, and it is working perfectly, however, it is skipping the first line completely. the very first line of the csv file isnt being sorted in the code...
however, if i go to the first line in notepad++ of the csv file and press enter to move the first line to line 2 and leave line 1 blank it works perfectly and reads everything...
any idea on why this might be happening?
br.readLine();
while ((line = br.readLine()) != null)
is how im writing it..
Because you're calling readLine() before the loop and throwing the result away.
Solution: don't.
Don't do like this. It is reading twice which is skipping the first line.
String policyUser;
while(reader.readLine() !=null){
policyUser = reader.readLine();
System.out.println(policyUser);
}
Do this:
while((policyUser=reader.readLine())!=null){
System.out.println(policyUser);
}
Related
How would this be written to be on a single line?
in_file = open(from_file)
indata = in_file.read
File.read("/path/to/file")
It will read whole file content and return it as a result.
open("README.md").read
For very small file, this is acceptable.
I have a text file as below
250788965731,20090906,200937,200909,621,SUNDAY,WEEKEND,ON-NET,MORNING,OUTGOING,VOICE,25078,PAY_AS_YOU_GO_PER_SECOND_PSB,SUCCESSFUL-RELEASEDBYSERVICE,5,0,1,6.25,635-10-104-40163.
I'm just a beginner in hadoop.I faced the following problem.
How do i print the entire line in my output file? As far as i know only A key & A Value can be written to the output file. How to write this entire line with many arguments in my output file. Or how do i write atleast a few arguments of it in a output file?
Use the TextOutputFormat and write the line as a Text writable as the key. Make the value null
context.write( new Text("your output line") , null);
I am learning Ruby and am messing with reading/writing files right now. When I create the file, 'filename', I can write to it with the .write() method. However, I cannot output the content to the terminal without reopening it after running .read() on it (see line 8: puts write_txt.read()). I have tried running line 8 multiple times, but all that does is output more blank lines. Without line 8, puts txt.read() simply outputs a blank line. The following code also works without the puts in line 8 (simply write_txt.read())
# Unpacks first argument to 'filename'
filename = ARGV.first
# Lets write try writing to a file
write_txt = File.new(filename, 'w+')
write_txt.write("OMG I wrote this file!\nHow cool is that?")
# This outputs a blank line THIS IS THE LINE IN QUESTION
puts write_txt.read()
txt = File.open(filename)
# This actually outputs the text that I wrote
puts txt.read()
Why is this necessary? Why is the file that has clearly been written to being read as blank until it is reopened after being read as blank at least once?
When you read or write to a file, there's an internal pointer called a "cursor" that keeps track of where in the file you currently are. When you write a file, the cursor is set to the point after the last byte you wrote, so that if you perform additional writes, they happen after your previous write (rather than on top of it). When you perform a read, you are reading from the current position to the end of the file, which contains...nothing!
You can open a file (cursor position 0), then write the string "Hello" (cursor position 6), and attempting to read from the cursor will cause Ruby to say "Oh hey, there's no more content in this file past cursor position 6", and will simply return a blank string.
You can rewind the file cursor with IO#rewind to reset the cursor to the beginning of the file. You may then read the file (which will read from the cursor to the end of the file) normally.
Note that if you perform any writes after rewinding, you will overwrite your previously-written content.
# Unpacks first argument to 'filename'
filename = ARGV.first
# Lets write try writing to a file
write_txt = File.new(filename, 'w+')
write_txt.write("OMG I wrote this file!\nHow cool is that?")
write_txt.rewind
puts write_txt.read()
Note, however, that it is generally considered bad practice to both read from and write to the same file handle. You would generally open one file handle for reading and one for writing, as mixing the two can have nasty consequenses (such as accidentally overwriting existing content by rewinding the cursor for a read, and then performing a write!)
The output is not necessarily written to the file immediately. Also, the pointer is at the end of the file, if you want to read while in read-write mode you have to reset it. You can simply close if you want to reopen it for reading. Try:
write_txt.write("OMG I wrote this file!\nHow cool is that?")
# This outputs a blank line THIS IS THE LINE IN QUESTION
write_txt.close
txt = File.open(filename)
puts txt.read()
I have a script that dumps data from a serial port to both a terminal and the harddrive. The output to the terminal looks fine, however the file write an ^M after each resulting in an extra newline for every other line.
The offending code:
# run and dump to file.
loop {
# output data to log file.
data = sp.read
data.delete!("\C-M") # Removes escape character.
if( data != "" )
puts data
File.open($log_file, 'a') { |f| f.write( data ) }
end
}
Example output:
On the terminal:
1
2
3
In the file
1
2
3
Edit: The solution is to run data.delete!("\C-M") after the read.
Try opening the data written to the file in ruby with read. I suspect the problem you have is with the carriage return characters that sometimes cause problems when transferring a file from windows to linux or when downloading files via some mail clients.
I don't know how your serial data looks like, but you can always do a chomp on data variable before writing. Try it and see how it goes.
Edit: If you want to remove the ^M, maybe you can try sp.read.tr("\r","")
I'm trying to read data from a text file and join it with a post string. When there's only one line in the file, it works fine. But with 2 lines, my request is failed. Is each_line reading the line break? How can I correct it?
File.open('sfzh.txt','r'){|f|
f.each_line{|row|
send(row)
}
I did bypass this issue with split and extra delimiter. But it just looks ugly.
Yes, each_line includes line breaks. But you can strip them easily using chomp:
File.foreach('test1.rb') do |line|
send line.chomp
end
Another way is to map strip onto each line as it is returned. To read a file line-by-line, stripping whitespace and do something with each line you can do the following:
File.open("path to file").readlines.map(&:strip).each do |line|
(do something with line)
end