Ruby: Finding Most Recently Modified File

Ruby: Finding most recently modified file

Dir.glob("*").max_by {|f| File.mtime(f)}

Ruby - Get the second most recent file from a directory?

You can do as below using Ruby 2.2.0, which added an optional argument to the methods Enumerable#max_by, Enumerable#min_by and Enumerable#min etc.

Dir.glob("./logs/*").max_by(2) {|f| File.mtime(f)}
# gives first 2 maximun.
# If you want the second most recent
Dir.glob("./logs/*").max_by(2) {|f| File.mtime(f)}.last

max_by(n) {|obj| block } → obj

If the n argument is given, minimum n elements are returned as an array.

How to find most recently modified file in a remote directory (via ssh)?

This is less a Net::SSH question as it is "What command can I issue to find the most recently modified file?"

SSH connections can issue a command, so once you know what command to send, or execute, you're done. I'd look at:

ls -Alt path/to/files | sed -n '2p'

Fleshing out something more usable results in:

require 'net/ssh'

HOST = 'hostname.domain'
USER = 'user'
PASSWORD = "password"

output = Net::SSH.start(HOST, USER, :password => PASSWORD) { |ssh|
  ssh.exec!('ls -alt . | grep pattern_to_find') 
}

puts output

Which, after filling in the fields with the right values and running it, connected to one of my hosts at work and returned something like:

drwxr-xr-x  11 xxxxxxxxxxxx xxxxxxxxx    4096 Oct  2 16:20 development

If you have multiple hits you need to retrieve, either expand the pattern after grep or discard the pipe to grep and parse your resulting output in Ruby once the command returns. You can also discard the t flag from ls if you want to sort locally, though it's a better idea to offload as much of the processing to the far-side host, rather than have it return a huge glob of data and process it locally. The less you return, the faster your overall code will be.

How to get last modified file in a directory to pass to system commands using Ruby?

There's no need to shell out to ls and parse its output at all. Ruby gives you standard library methods to fetch directory contents and examine file mtimes. Here's a ruby method to return the name of a file in a directory with the latest mtime.

def last_modified_in dir
  Dir.glob( File.join( dir,'*' ) ).
  select  {|f| File.file? f }.
  sort_by {|f| File.mtime f }.
  last
end

irb> system 'mkdir -p /tmp/foo'
irb> system 'rm /tmp/foo/*'
irb> ('a'..'c').each { |f| system "touch /tmp/foo/#{f}"; sleep 1; }
irb> puts last_modified_in '/tmp/foo'
# => /tmp/foo/c

Find date file was last modified

You can pass it a string of the file name.

irb(main):001:0> File.mtime("Gemfile")
=> 2016-08-22 13:54:43 -0700

To reference files from within rails you can use Rails.root.join:

gemfile = Rails.root.join("Gemfile")
=> #<Pathname:/Users/username/projects/appname/Gemfile>

File.mtime(gemfile)
=> 2016-08-22 13:54:43 -0700

The docs also mention you can pass it an IO object.

How do I find the files changed in a commit using Rugged?

You can use Rugged::Commit#diff to get the changes between the commit and its first parent or another Rugged::Commit or Rugged::Tree.

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