I am practicing Ruby, and I am trying to copy contents from file "from" to file "to". can you tell me where I did it wrong?
thanks !
from = "1.txt"
to = "2.txt"
data = open(from).read
out = open(to, 'w')
out.write(data)
out.close
data.close
Maybe I am missing the point, but I think writing it like so is more 'ruby'
from = "1.txt"
to = "2.txt"
contents = File.open(from, 'r').read
File.open(to, 'w').write(contents)
Personally, however, I like to use the Operating systems terminal to do File operations like so. Here is an example on linux.
from = "1.txt"
to = "2.txt"
system("cp #{from} #{to}")
And for Windows I believe you would use..
from = "1.txt"
to = "2.txt"
system("copy #{from} #{to}")
Finally, if you were needing the output of the command for some sort of logging or other reason, I would use backticks.
#A nice one liner
`cp 1.txt 2.txt`
Here is the system and backtick methods documentation.
http://ruby-doc.org/core-1.9.3/Kernel.html
You can't perform data.close — data.class would show you that you have a String, and .close is not a valid String method. By opening from the way you chose to, you lost the File reference after using it with your read. One way to fix that would be:
from = "1.txt"
to = "2.txt"
infile = open(from) # Retain the File reference
data = infile.read # Use it to do the read
out = open(to, 'w')
out.write(data)
out.close
infile.close # And finally, close it
Related
I'm reading a text file which has instructions on each line. I want to assign the text on each line to it's own variable. When I do this, the value returned is nil but when I output the value of readlines[n] it is correct.
e.g.
# Using the variable (incorrect result)
puts current_zone_size
>
e.g.
# Using readlines after variable assignment (incorrect result)
current_zone_size = instructions.readlines[0]
instructions.readlines[0]
>
e.g.
# Using readlines (correct result)
instructions.readlines[0]
> 8 10
This is my code:
instructions = File.open("operator-input.txt", "r")
current_zone_size = instructions.readlines[0]
rover_init_location_orientation = instructions.readlines[1]
rover_movements = instructions.readlines[2]
This is the text in the file being read:
8 10
1 2 E
MMLMRMMRRMML
Edit:
Is the file being closed? Is this the reason I can't assign values from File.readlines[n] to variables if I'm not doing the variable assignment from within a block?
Also, the file will only ever have three lines which is why I'm not using a loop to read the lines.
IO#readlines reads all the lines in the file. It should not come as a surprise that, in order to read all the lines in the file, it has to read the entire file.
So, where is the file pointer after you read the entire file? It is at the end of the file.
What happens if you call IO#readlines the second time, when the file pointer is still at the end of the file? It will start reading at the position of the file pointer, which means it will read an empty file.
Therefore, if you want to do it the way you are doing it, you need to reset the file pointer to the beginning of the file every time you call IO#readlines:
instructions = File.open('operator-input.txt', 'r')
current_zone_size = instructions.readlines[0]
instructions.pos = 0
rover_init_location_orientation = instructions.readlines[1]
instructions.pos = 0
rover_movements = instructions.readlines[2]
Note also that you are leaking resources: you never close the file, so it will only by closed at the earliest by Ruby when the instructions variable gets out of scope and the File instance gets garbage-collected, and at the latest by the OS automatically when your Ruby process exits, which may be a long time later. So, your code should rather be:
instructions = File.open('operator-input.txt', 'r')
current_zone_size = instructions.readlines[0]
instructions.pos = 0
rover_init_location_orientation = instructions.readlines[1]
instructions.pos = 0
rover_movements = instructions.readlines[2]
instructions.close
In general, it is much better to use the block form of File::open, which closes the file handle automatically for you at the end of the block, and also ensures that this happens even in the case of complex control flow, errors, or exceptions:
File.open('operator-input.txt', 'r') do |instructions|
current_zone_size = instructions.readlines[0]
instructions.pos = 0
rover_init_location_orientation = instructions.readlines[1]
instructions.pos = 0
rover_movements = instructions.readlines[2]
end
Note, however, that what you want to do is horribly inefficient: you read the entire file, then take the first line, throw the rest away. Then you read the entire file again, take the second line, throw the rest away. Then you read the entire file again, take the third line, throw the rest away.
It makes much more sense to read the entire file once and then take the lines you need. Something like this:
File.open('operator-input.txt', 'r') do |instructions|
current_zone_size, rover_init_location_orientation, rover_movements =
instructions.readlines
end
However, in the case where all you do is open the file, read all lines, then immediately close it again, you should rather use the IO::readlines method instead of IO#readlines, since it does all three things for you in one call:
current_zone_size, rover_init_location_orientation, rover_movements =
File.readlines('operator-input.txt')
I ended up reading all the lines at once, now I'm able to set each variable outside of a block. Like this:
instructions = File.readlines "operator-input.txt"
current_zone_size = instructions[0]
rover_init_location_orientation = instructions[1]
rover_movements = instructions[2]
e.g.
puts current_zone_size
> 8 10
As part of my larger program, I want to create a logfile with the current time & date as part of the title. I can create it as follows:
malwareLog = open(datetime.datetime.now().strftime("%Y%m%d - %H.%M " + pcName + " Malware scan log.txt"), "w+")
Now, my app is going to call a number of other functions, so I'll need to open the file, write some output to it and close the file, several times. It doesn't seem to work if I simply go:
malwareLog.open(malwareLog, "a+")
or similar. So how should I open a dynamically created txt file that I don't know the actual filename for...?
When you create malwareLog object, it has name attribute which contains the file name.
Here's an example: (my test is your malwareLog)
import random
test = open(str(random.randint(0,999999))+".txt", "w+")
test.write("hello ")
test.close()
test = open(test.name, "a+")
test.write("world!")
test.close()
with open(test.name, "r") as f: print(f.read())
You also can store the file name in a variable before or after creating the file.
###Before
file_name = "123"
malwareLog = open(file_name, "w")
###After
malwareLog = open(random.randint(0,999999), "w")
file_name = malwareLog.name
I have two questions regarding the following code:
import subprocess
macSource1 = (r"\\Server\path\name\here\dhcp-dump.txt")
macSource2 = (r"\\Server\path\name\here\dhcp-dump-ops.txt")
with open (r"specific-pcs.txt") as file:
line = []
for line in file:
pcName = line.strip().upper()
with open (macSource1) as source1, open (macSource2) as source2:
items = []
for items in source1:
if pcName in items:
items_split = items.rstrip("\n").split('\t')
ip = items_split[0]
mac = items_split[4]
mac2 = ':'.join(s.encode('hex') for s in mac.decode('hex')).lower() # Puts the :'s between the pairs.
print mac2
print pcName
print ip
Firstly, as you can see, the script is searching for the contents of "specific-pcs.txt" against the contents of macSource1 to get various details. How do I get it to search against BOTH macSource1 & 2 (as the details could be in either file)??
And secondly, I need to have a stricter matching process as at the moment a machine called 'itroom02' will not only find it's own details, but also provide the details for another machine called '2nd-itroom02'. How would I get that?
Many thanks for your assistance in advance!
Chris.
Perhaps you should restructure it a bit more like this:
macSources = [ r"\\Server\path\name\here\dhcp-dump.txt",
r"\\Server\path\name\here\dhcp-dump-ops.txt" ]
with open (r"specific-pcs.txt") as file:
for line in file:
# ....
for target in macSources:
with open (target) as source:
for items in source:
# ....
There's no need to do e.g. line = [] immediately before you do for line in ...:.
As far as the "stricter matching" goes, since you don't give examples of the format of your files, I can only guess - but you might want to try something like if items_split[1] == pcName: after you've done the split, instead of the if pcName in items: before you split (assuming the name is in the second column - adjust accordingly if not).
I'm capturing/creating user entered text into files from my app, attempting to temporarily store them in my Heroku tmp directory, then upload them to a cloud service such as Google Drive.
In using Tempfile I can successfully upload, but when using File.open I get the following error when attempting to upload:
ArgumentError (wrong number of arguments (1 for 0))
The error is on the call:
#client.upload_file_by_folder_id(save_path, #folder_id)
Where #client is a session with the cloud service, save_path is the location of the attached file for upload and #folder_id is the folder they should go into.
When I use Tempfile.new I am successful in doing so:
tempfile = Tempfile.new([final_filename, '.txt'], Rails.root.join('tmp','text-temp'))
tempfile.binmode
tempfile.write msgbody
tempfile.close
save_path = tempfile.path
upload_file = #client.upload_file_by_folder_id(save_path, #folder_id)
tempfile.unlink
File.open code is:
path = 'tmp/text-temp'
filename = "#{final_filename}.txt"
save_path = Rails.root.join(path, filename)
File.open(save_path, 'wb') do |file|
file.write(msgbody)
file.close
end
upload_file = #client.upload_file_by_folder_id(save_path, #folder_id)
File.delete(save_path)
Could it be that the File.path is a string, and Tempfile.path is the full path (but not as a string)? When I put out each, they look identical.
I'd like to use File as I don't want to change the filename of the existing attachments I'm uploading, whereas Tempfile appends to the filename.
Any and all assistance is greatly appreciated. Thanks!
In order for it to work using File, I needed to set the save_path to a string:
save_path.to_s
I have downloaded a set of html files and saved the file paths which I saved them to in a .txt file. It has each path on a new line. I wanted to look at the first file in the list and then itterate through the whole list, opening the files and extracting data before going on to the next file.
My code works fine with a single path put in directly (for the first file) as:
path = r'C:\path\to\file.html'
and works if I itterate through the text file using:
file_list_fp = r'C:\path\to\file_with_pathlist.txt'
with open(file_list_fp, 'r') as file_list:
for filepath in file_list:
pathend = filepath.find('\n')
path = file[:pathend]
q = open(path, 'r').read()
but it fails when I try getting a single path using either:
with open(file_list_fp, 'r') as file_list:
path_n = file_list.readline()
end = path_n.find('\n')
path_bad1 = path_n[:end]
or:
with open(file_list_fp, 'r') as file_list:
path_bad2 = file_list.readline().split('\n')[0]
With these two my code exits just after that point. I can't figure out why. Any pointers very welcome. (I'm using Python 3.3.1 on windows.)