[PATCH] test: allow setting TAIL env to watch error logs

[Eric Wong <e@80x24.org>]

Setting TAIL=1 will automatically use the portable "tail -f".
This can be helpful in diagnosing failures during development.

GNU tail users may set TAIL="tail -F" (or "gtail -F")
to use the "-F" ("--follow=name") option to track changes
across SIGUSR1 log reopening testing.
---
 test/server_helper.rb | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/test/server_helper.rb b/test/server_helper.rb
index cb11e79..9ef15c6 100644
--- a/test/server_helper.rb
+++ b/test/server_helper.rb
@@ -65,12 +65,29 @@ def server_helper_teardown
     @srv.close if defined?(@srv) && !@srv.closed?
     @ru.close! if defined?(@ru) && @ru
     check_err if defined?(@err)
+    Timeout.timeout(30) do
+      Process.kill(:TERM, @tail_pid)
+      Process.waitpid(@tail_pid)
+    end if @tail_pid
   end
 
   def server_helper_setup
     @srv = TCPServer.new(ENV["TEST_HOST"] || "127.0.0.1", 0)
     @err = tmpfile(%w(srv .err))
     @ru = nil
+    @tail_pid = nil
+    case tail = ENV['TAIL']
+    when '1'
+      tail = 'tail -f' # POSIX
+    when nil, '0'
+      tail = nil
+    # else : allow users to specify 'tail -F' or 'gtail -F' for GNU
+    end
+    if tail
+      cmd = tail.split(/\s+/)
+      cmd << @err.path
+      @tail_pid = spawn(*cmd)
+    end
   end
 
   def mkserver(cfg, srv = @srv)
-- 
EW