Difference between the access modes of the `File` object (ie. w+, r+)

Question

When using files in Ruby, what is the difference between the r+ and w+ modes? What about the a+ mode?

Answer 1

Access modes r+, w+ and a+ opens the file in read and write mode, but with the following difference:

r+ starts at beginning of file, but will not create a new file if it doesn't exists.

w+ truncates existing file to zero length if the file exists, otherwise creates a new file.

a+ starts at end of file if file exists, otherwise creates a new file.