Ruby

Add an iterator for each file supplied on the command line, or STDIN. ARGF#each_io

Current Status¶

Often, we need to do something with individual files ARGF knows about rather than the concatenation of them. We can combine ARGF#to_io and ARGF#skip to achieve this as follows:

while (file = ARGF.to_io) break if file.closed? || file.eof? csv = CSV.new(file) csv.each { |line| p line } ARGF.skip end 

Proposal¶

Add an iterator ARGF#each_io to do the above. The above example would then become:

ARGF.each_io do |io| csv = CSV.new(io) csv.each { |line| p line } end 

The name is #each_io. We could call it #each_file as well, but ARGF#to_io emits an IO object when the current file is STDIN.

Implementation¶

A cursory ruby implementation is below. Could better handle the STDIN edge case, and would probably be better off being written in C.

def ARGF.each_io(&fn) raise 'ARGF#each_io needs a block!' unless block_given? while (file = to_io) break if file.closed? || file.eof? fn.call(file) # File was STDIN, no need to go any further. break if file.class == IO skip end end 

Issues¶

• Handling the STDIN edge case is ugly.
• Not clear if eof? checking for STDIN should be left up to the user instead.
• A real world implementation should return a proper iterator instead of the above.