send SIGTTOU to forked process?

anna has asked for the wisdom of the Perl Monks concerning the following question:

Hi everyone. I am trying to write a simple shell interpreter. And I want it to act like bash, i.e. when user wants to run a process in the background, and the process tries to access stdin or stdout, the shell sends it SIGTTOU. So, I write:

...
$pid = fork()
if($pid == 0)
{
    if($command =~ /\&$/) 
    {
        if(-t STDIN and -t STDOUT)
        {
           kill TTOU =>$pid;
           exec($command);
        }
    }
    else 
    {
        ...
    }
}
[download]

As I expect, it kills the forked process without executing the command. Can anyone help me with the problem?

thanks in advance, anna.

Comment on send SIGTTOU to forked process? Download Code

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Re: send SIGTTOU to forked process? by ikegami (Patriarch) on Dec 11, 2009 at 08:30 UTC
It seems to stop the parent too. I don't know if this is the proper workaround, but this works: `use Time::HiRes qw( sleep ); my $pid = fork(); die $! if !defined($pid); if ($pid == 0) { for (1..8) { sleep(.250) if $_ != 1; print(time(), "\n"); } } else { $SIG{TTOU}='IGNORE'; sleep 1; kill TTOU => $pid or die $!; sleep 3; kill CONT => $pid or die $!; waitpid($pid, 0); }` [download] `1260520147 1260520147 1260520148 1260520148 1260520151 1260520151 1260520152 1260520152` [download] And it also works if the child is the one to send the signal. `use Time::HiRes qw( sleep ); my $pid = fork(); die $! if !defined($pid); if ($pid == 0) { for (1..2) { kill TTOU => 0 or die $! if $_ != 1; for (1..4) { sleep(.250) if $_ != 1; print(time(), "\n"); } } } else { $SIG{TTOU}='IGNORE'; sleep 4; kill CONT => $pid or die $!; waitpid($pid, 0); }` [download] `1260520571 1260520572 1260520572 1260520572 1260520575 1260520576 1260520576 1260520576` [download]	[reply] [d/l] [select]
Re: send SIGTTOU to forked process? by ikegami (Patriarch) on Dec 11, 2009 at 08:04 UTC
This works: `$ perl -le'kill TTOU => 0 or die $!; print "done"' [1]+ Stopped perl -le'kill TTOU => 0 or die $!; print "done"' $ fg perl -le'kill TTOU => 0 or die $!; print "done"' done` [download] Check for an error. If there's no error, it's not a problem sending the signal aka not a Perl problem.	[reply] [d/l]
Re: send SIGTTOU to forked process? by Anonymous Monk on Dec 11, 2009 at 07:08 UTC
kill takes numbers as arguments	[reply]
Re^2: send SIGTTOU to forked process? by ikegami (Patriarch) on Dec 11, 2009 at 08:14 UTC
It's perfectly happy with signal names too	[reply]