How to get filename without extension from file path in Ruby

Try File.basename

Returns the last component of the filename given in file_name, which must be formed using forward slashes (``/’’) regardless of the separator used on the local file system. If suffix is given and present at the end of file_name, it is removed.

File.basename("/home/gumby/work/ruby.rb")          #=> "ruby.rb"
File.basename("/home/gumby/work/ruby.rb", ".rb")   #=> "ruby"

In your case:

File.basename("C:\\projects\\blah.dll", ".dll")  #=> "blah"

require 'pathname'

Pathname.new('/opt/local/bin/ruby').basename
# => #<Pathname:ruby>

I haven't been a Windows user in a long time, but the Pathname rdoc says it has no issues with directory-name separators on Windows.

In case the extension is not known (it needs the / separator):

irb(main):024:0> f = 'C:\foobar\blah.txt'.gsub("\\","/")
=> "C:/foobar/blah.txt"
irb(main):027:0> File.basename(f,File.extname(f))
=> "blah"