Searching a folder and all of its subfolders for f

问题:

I am trying to search for all files of a given type (say .pdf) in a given folder and copy them to a new folder. What I need to be able to do is to specify a root folder and search through that folder and all of its subfolders for any files that match the given type (.pdf). Can anyone give me a hand on how I should search through the root folder's subfolders and their subfolders and so on. It sounds like a recursive method would do the trick here, but I cannot implement one correctly? (I am implementing this program in ruby by the way).

回答1:

You want the Find module. Find.find takes a string containing a path, and will pass the parent path along with the path of each file and sub-directory to an accompanying block. Some example code:

require 'find'

pdf_file_paths = []
Find.find('path/to/search') do |path|
  pdf_file_paths << path if path =~ /.*\.pdf$/
end

That will recursively search a path, and store all file names ending in .pdf in an array.

回答2:

Try this:

Dir.glob("#{folder}/**/*.pdf")

which is the same as

Dir["#{folder}/**/*.pdf"]

Where the folder variable is the path to the root folder you want to search through.

回答3:

If speed is a concern, prefer Dir.glob over Find.find.

Warming up --------------------------------------
           Find.find   124.000  i/100ms
            Dir.glob   515.000  i/100ms
Calculating -------------------------------------
           Find.find      1.242k (± 4.7%) i/s -      6.200k in   5.001398s
            Dir.glob      5.249k (± 4.5%) i/s -     26.265k in   5.014632s

Comparison:
            Dir.glob:     5248.5 i/s
           Find.find:     1242.4 i/s - 4.22x slower

 

require 'find'
require 'benchmark/ips'

dir = '.'

Benchmark.ips do |x|
  x.report 'Find.find' do
    Find.find(dir).select { |f| f =~ /\*\.pdf/ }
  end

  x.report 'Dir.glob' do
    Dir.glob("#{dir}/**/*\.pdf")
  end

  x.compare!
end

Using ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin15]

回答4:

As a small improvement to Jergason and Matt's answer above, here's how you can condense to a single line:

pdf_file_paths = Find.find('path/to/search').select { |p| /.*\.pdf$/ =~ p }

This uses the Find method as above, but leverages the fact that the result is an enumerable (and as such we can use select) to get an array back with the set of matches