Check out example codes for "ruby File.open options". It will help you in understanding the concepts better.
Code Example 1
#"r" Read-only, starts at beginning of file (default mode). #"r+" Read-write, starts at beginning of file. #"w" Write-only, truncates existing file # to zero length or creates a new file for writing. #"w+" Read-write, truncates existing file to zero length # or creates a new file for reading and writing. #"a" Write-only, each write call appends data at end of file. # Creates a new file for writing if file does not exist. #"a+" Read-write, each write call appends data at end of file. # Creates a new file for reading and writing if file does # not exist.
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