System is a blocking call. Here is the begining of the man page for lockfile. Does that help?

       lockfile can be used  to  create  one  or  more  semaphore
       files.   If  lockfile can't create all the specified files
       (in the specified order), it waits sleeptime (defaults  to
       8)  seconds and retries the last file that didn't succeed.
       You can specify the number of retries to do until  failure
       is  returned.   If  the  number of retries is -1 (default,
       i.e., -r-1) lockfile will retry forever.
[download]

So it is not able to create the file and it retries forever. Actually you are setting -2 as the retry interval and trying to set a max of 5 retries so it sould return after 10 seconds but it is not. GOK. Why shell out to create lockfiles anyway? Why not just do it native say like

sysopen($fh, "$dir/$name", O_CREAT | O_EXCL | O_RDWR, 0600);
[download]

>>Why shell out to create lockfiles anyway?

I didn't write it, and I don't know Perl very well at all.

>>Why not just do it native say like

sysopen($fh, "$dir/$name", O_CREAT | O_EXCL | O_RDWR, 0600);
[download]

Thanks for supplying the code. I don't know why the person wanted to lock the file. Here is a bigger snippet of what is happening, down to the unlink, which I think is like the "unlock" ??

system ("lockfile -2 -r 5 $base_dir/.lock")  == 0
        or diehtml("Lock error: ", $? >> 8, "\n");
        # TODO stop stderr of system

    # create unique suffix
    if (-f "$base_dir/$seq_file") {
        open(SEQ, "+<$base_dir/$seq_file")
            or diehtml("Error opening seq file: $!\n");
        $seq = ;
        seek SEQ, 0, 0;
    } else {
        open(SEQ, ">$base_dir/$seq_file")
            or diehtml("Error creating seq file: $!\n");
        $seq = 0;
    }
    
    $outfile .= sprintf "%7.7d", $seq;
    $ordernumber = $seq;    #store this order no. before 'next' is cal
+c.
    print SEQ ++$seq;
    close SEQ or warn "Something wrong closing seq: $!\n";
    unlink "$base_dir/.lock" or diehtml("Unlock error: $!\n");

    open(ORDERFILE, ">$outfile")
        or diehtml("Can't open order records: $!\n");

    print ORDERFILE @_;
    close ORDERFILE or warn "Something fishy with closing the order: $
+!\n";
}
[download]

The file SEQ, is just a line line ASCII file with the next order number in it.

Peter

I didn't write it, and I don't know Perl very well at all.

We know. Regardless you have come to the right place for help.

The purpose of a lockfile is to tell other processes (ie copies of a CGI) to bugger off and wait their turn.

Anyway here is a pure Perl replacement that is identical to the lockfile call (well it is not IDENTICAL) because this actually works as the system call to lockfile should....

my $got_lock;
use Fcntl;   # to get constants for O_CREAT | O_EXCL | O_RDWR
for ( 0 .. 5 ) {
    if ( sysopen(my $fh, "$base_dir/.lock", O_CREAT | O_EXCL | O_RDWR,
+ 0600) ) {
        $got_lock = 1;
        close $fh;
      last;
    }
    sleep 2;
}
diehtml("Lock error $!\n") unless $got_lock;
[download]

That should be a cut and paste replacement for this:

system ("lockfile -2 -r 5 $base_dir/.lock")  == 0
        or diehtml("Lock error: ", $? >> 8, "\n");
        # TODO stop stderr of system
[download]

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

I don't know why the person wanted to lock the file.

I actually found a post on comp.lang.perl.misc that was from the guy that wrote it; here is his algorithm:

enter program
while (1)
   look for lockfile
   if lockfile does not exist exit
   sleep 5 seconds
}
create lockfile

..... do normal program stuff ......

unlink lockfile
exit
[download]

However, if the process died before removing the lock, it crashed the web server. The post was 7 years ago, so no doubt what has been suggested here will be _much_ better. :)

Peter

>>Suggestion. SSH into the shell and deal with your server like a (man/woman/real hacker).

Okay, I will have to leave it until the morning, it's late here (down under), and the pwd for SSH access is on another computer.

Possibly the code needs rewriting anyway. Thanks to you all for your help, ... wow, I have never received such fast responses. :)

Peter

Hi tachyon,

Thanks for sorting out the lockfile problem. I will either use this one you supplied

my $got_lock;
use Fcntl;   # to get constants for O_CREAT | O_EXCL | O_RDWR
for ( 0 .. 5 ) {
    if ( sysopen(my $fh, "$base_dir/.lock", O_CREAT | O_EXCL | O_RDWR,
+ 0600) ) {
        $got_lock = 1;
        close $fh;
      last;
    }
    sleep 2;
}
diehtml("Lock error $!\n") unless $got_lock;
[download]

.. or the "fully blown" lockfile code you supplied in your other post ..You either have to delete it by hand or do something like this:

I consider the lockfile problem sorted out now, thanks. Because of the problems now with "opens", I would to replace code like this:

open(ORDERFILE, ">$outfile")
        or diehtml("Can't open order records: $!\n");
[download]

with (native) code of the format:

sysopen($fh, "$dir/$name", O_CREAT | O_EXCL | O_RDWR, 0600);
[download]

... would it be something like:

$fh = "ORDERFILE";
sysopen($fh, "$outfile", O_CREAT | O_EXCL | O_RDWR, 0600)
        or diehtml("Can't open order records: $!\n");
[download]

Just a wild guess. :)

Peter

No :-)

This code is fine for what it does:

open        # open a file for read or write
(
ORDERFILE  # onto a FILEHANDLE called ORDERFILE
,
"
>          # > means write to the file, create if does not exist
           # Note all previous content will be deleted 
           # if this file exists >> means append to the end
$outfile   # full or relative path to file
"
)
or         # if the open works it returns true so we never do the next
+ bit
diehtml()  # print an error message
[download]

You don't wanna touch anything in the demon code. It was for illustrative purposes and is not relevant to your problem provided you are happy that the code you have worked just replace the lockfile code.

In this code:

$fh = "ORDERFILE";
sysopen($fh, "$outfile", O_CREAT | O_EXCL | O_RDWR, 0600)
        or diehtml("Can't open order records: $!\n");
[download]

You don't need to set $fh to a string. It will just get overwritten in the open. A FILEHANDLE is a type of perl internal object (like a scalar) and the reference to it is held in the $fh var. To illustrate the syntax:

open $fh, ">$file" or die "Can't write $file $!\n";
print $fh "here is some data\n";
close $fh;
[download]

Same with sysopen but I can't be bothered to type that much.

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

If your system call is not returning, that means the lockfile process is not returning. Take a look at that.

File locking is a tricky field that is very susceptible to portability issues. You might have been bitten by one of them.

Hi,

Yikes, .. I just used CPanel to check on the installed Perl modules, and I couldn't find lockfile or system, so I guess I'm going to have to change the code.

Thanks,

Peter

Whoa, hang on there.

system is a perl built-in function, so you do not need any modules installed to have it available.

lockfile is part of your operating system software (well, that's not technically completely accurate, but close enough), so it has nothing to do with Perl in itself.

Back out of that alley you've gone down and look for the solution in another direction :). Your problem is most probably situated in different behaviour of lockfile between your original and current systems.

CU
Robartes-

lockfile(1) is part of the OS. system() is part of Perl. Neither are Perl modules. Regardless of your lack of understanding of what your code is doing to what and where your analysis of the required actions is correct.

Suggestion. SSH into the shell and deal with your server like a (man/woman/real hacker).

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

You're running under taint mode and don't appear to be setting $ENV{PATH}. You can't execute external programs under taint without setting the PATH env var. Better still is to write the lockfile code in pure Perl.

You're running under taint mode and don't appear to be setting $ENV{PATH}. You can't execute external programs under taint without setting the PATH env var.

How do I set $ENV{PATH} , and what should I set it to ?

Better still is to write the lockfile code in pure Perl.

The lockfile part of the code is now in pure Perl

Thanks,

Peter

On most *nix systems, the PATH environment var is a colon-delimited list of directories where programs can be executed without specifying the full path. Setting it to /bin:/usr/bin is typical.

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated

With replacing the code, the script is getting further now. It is stopping or just sitting at the following block of code

open(ORDERFILE, ">$outfile")
        or diehtml("Can't open order records: $!\n");

    print ORDERFILE @_;
    close ORDERFILE or warn "Something fishy with closing the order: $
+!\n";
[download]

The value of the variable $outfile has been printed before the above code, and is "/home/username/public_html/.orders/2003-10-01-0001130"

There were other "open" commands performed successfully, prior to _this_ open stopping ?

Peter

Should I replace the following with a 'sysopen' function, like in the locking example ?

open(ORDERFILE, ">$outfile")
[download]

Peter

Hi,

Well, that worked, it has now actually created the ascii order file, and gone much further. Now it is stopping/doing nothing here

open(SENDMAIL, '|/usr/sbin/sendmail -oi -t')
   or (unlink ($outfile),
    diehtml("Can't fork for sendmail: $!\n"));
[download]

So, .... it looks like the moral to this story is replace ALL open() with sysopen(), using the parameters and examples as supplied, to fix the locking example.

If I used this code as a template for all the file opens

my $got_lock;
use Fcntl;   # to get constants for O_CREAT | O_EXCL | O_RDWR
for ( 0 .. 5 ) {
    if ( sysopen(my $fh, "$base_dir/.lock", O_CREAT | O_EXCL | O_RDWR,
+ 0600) ) {
        $got_lock = 1;
        close $fh;
      last;
    }
    sleep 2;
}
diehtml("Lock error $!\n") unless $got_lock;
[download]

.... would I need the 'sleep', and what does the FOR contruct do ? Does it try for 6 times ?? Please pardon my ignorance, I'm _very_ much a novice at Perl. :)

Thanks,

Peter