Using $SIG{__DIE__} and exec

[Krel]

My CGI script accesses a mysql database, and it won't work in mysqld.exe isn't running. Sometimes, that program gets is shut down for various reasons. In my script, I have it script die if it can't connect to the database, and then I set $SIG{__DIE__} to exec mysqld.exe as the last thing it does.

When the script dies because the database connection didn't work, mysqld.exe is started as I want. However, I also want it to display a message in the browser indicating that refreshing your screen will fix the problem (because this time mysqld.exe will be running). However, my script just keeps running and eventually times out without showing any output. As I said, though, the exec is done successfully.

$|  = 1;  
$SIG{__DIE__} = sub { 
  print "Content-type: text/html\n\n $_[0]"; 
  exec 'C:\apache\mysql\bin\mysqld.exe' if $_[0]=~ /MySQL/; 
};
my $DatabaseConnection  = DBI->connect('dbi:mysql:lotto649') or die "MySQL Connection Failed.  Please use your refresh button and everything should work normally. $!";

 

[justice41]

You should read the perldoc (

http://www.perldoc.com/perl5.6.1/pod/func/exec.html)

about exec if you really want to use it. What you probably want to use is system() instead. The perldoc explains why. The essential reason is that exec never returns, this is why your program times out.

jaa

 

[Krel]

It does the exact same thing with system()... Could it be because mysqld.exe never really "quits" (it just stays there), so the perl program never gets a response and thus times out? If so, how could I get around this?

 

[Krel]

Oh yeah, and I tried using backticks in a void context and that timed out as well. The script does NOT time out if I don't use system, exec or backticks, so I'm certain those are the problem. All three methods do start the program correctly, though.

 

[JustKIDn]

Just thinking out loud here.

Is there a way to check to see if mysqld.exe is running before you try to connect and then if it's not then start it?

tgus

____________________________________________________
A father's calling is eternal, and its importance transcends time.

 

[Krel]

I thought about that, but I would probably run into the same problems trying to start mysqld.exe and run the script as I'm having now.

Basically, is there any way that perl can execute a program without expecting a waiting for any kind of return value?