[ruby-core:23309] Re: [Bug #1403] Process.daemon should do a double fork to avoid problems with controlling terminals

In article <[e-mail]>,
  Nobuyoshi Nakada <[e-mail]> writes:

>> The second fork ensures that the process (the grandchild of the  
>> original process) is no longer a session leader and therefore can't  
>> acquire a controlling terminal by opening a tty device.
>
> Could you show concrete example?

% ruby -v -rpty -e '
m, s = PTY.open
Process.daemon(true,true)
system("ps cj#{$$}")
open(s.path)
system("ps cj#{$$}")
'; sleep 1
ruby 1.9.2dev (2009-03-13 trunk 22936) [i686-linux]
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
    1  6153  6153  6153 ?           -1 Rsl   1000   0:00 ruby
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
    1  6153  6153  6153 pts/11    6153 Rs+   1000   0:00 ruby

This request means that 2nd TTY field should be "?" as 1st.

fork after Process.daemon does that.

% ruby -v -rpty -e '
m, s = PTY.open
Process.daemon(true,true)
exit if fork != nil
system("ps cj#{$$}")
open(s.path)
system("ps cj#{$$}")
'; sleep 1
ruby 1.9.2dev (2009-03-13 trunk 22936) [i686-linux]
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
    1  6241  6238  6238 ?           -1 Sl    1000   0:00 ruby
 PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
    1  6241  6238  6238 ?           -1 Sl    1000   0:00 ruby

I'm not sure this is a bug of daemon() in glibc or not.
[ruby-talk:111518]
-- 
Tanaka Akira