.size是什么意思

Question

What does target.size mean in the below code and what does w mean that is next to the filename? And when I remove w or .size the program what does that mean?

filename = ARGV.first
    script = $0

    puts "We're going to erase #{filename}."
    puts "If you don't wnat that, hit CTRL-C (^C)."
    puts "If you do want that, hit RETURN."

    print "? "
    STDIN.gets

    puts "Opening the file..."
    target = File.open(filename,'w')

    puts "Truncating the file. Goodbye!"
    target.truncate(target.size)

    puts "Now I'm going to ask you for three lines."

    print "line 1: "; line1 = STDIN.gets.chomp()
    print "line 2: "; line2 = STDIN.gets.chomp()
    print "line 3: "; line3 = STDIN.gets.chomp()

    puts "I'm going to write these to the file"

    target.write(line1)
    target.write("\n")
    target.write(line2)
    target.write("\n")
    target.write(line3)
    target.write("\n")
    puts "And finally, we Close it"
    target.close()

Answer 1

File.open(filename,'w') gives you a File object, which is assigned to the local variable target . target.size means actually File#size , which Returns the size of file in bytes. If you don't supply the mode as 'w' , then the file will be opened with mode 'r' , which is a default mode.

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Read IO Open Mode :

"w" :

Write-only, truncates existing file to zero length or creates a new file for writing.

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Explanation of the line target.truncate(target.size) .

Here you actually called File#truncate , what this method does is Truncates file to at most integer bytes . That means you are deleting the file contents fully and making the file size as zero .