[GR-27327] Fix redirect fd specs

PullRequest: truffleruby/2137

Author: eregon

spec/mspec/lib/mspec/helpers/io.rb

@@ -85,7 +85,3 @@ def new_io(name, mode = "w:utf-8")
     File.new(name, mode)
   end
 end
-
-def find_unused_fd
-  Dir.entries("/dev/fd").map(&:to_i).max + 1
-end

spec/ruby/core/process/exec_spec.rb

@@ -193,9 +193,11 @@
           map_fd_fixture = fixture __FILE__, "map_fd.rb"
           cmd = <<-EOC
             f = File.open(#{@name.inspect}, "w+")
-            child_fd = f.fileno + 1
-            File.open(#{@child_fd_file.inspect}, "w") { |io| io.print child_fd }
-            Process.exec "#{ruby_cmd(map_fd_fixture)} \#{child_fd}", { child_fd => f }
+            File.open(#{__FILE__.inspect}, "r") do |io|
+              child_fd = io.fileno
+              File.open(#{@child_fd_file.inspect}, "w") { |io| io.print child_fd }
+              Process.exec "#{ruby_cmd(map_fd_fixture)} \#{child_fd}", { child_fd => f }
+            end
             EOC
 
           ruby_exe(cmd, escape: true)

spec/ruby/core/process/spawn_spec.rb

@@ -706,13 +706,15 @@ def child_pids(pid)
       end
 
       it "maps the key to a file descriptor in the child that inherits the file descriptor from the parent specified by the value" do
-        child_fd = find_unused_fd
-        args = ruby_cmd(fixture(__FILE__, "map_fd.rb"), args: [child_fd.to_s])
-        pid = Process.spawn(*args, { child_fd => @io })
-        Process.waitpid pid
-        @io.rewind
-
-        @io.read.should == "writing to fd: #{child_fd}"
+        File.open(__FILE__, "r") do |f|
+          child_fd = f.fileno
+          args = ruby_cmd(fixture(__FILE__, "map_fd.rb"), args: [child_fd.to_s])
+          pid = Process.spawn(*args, { child_fd => @io })
+          Process.waitpid pid
+          @io.rewind
+
+          @io.read.should == "writing to fd: #{child_fd}"
+        end
       end
     end
   end