I have a Perl script that works on non-darwin Mac OS X environments and I think I have narrowed down the issue to a file locking problem.
In other linux environments, the flock struct is defined differently. I have adjusted this via the reference for Mac OS X fcntl(2) man page. The struct is defined as:
I am using the flock as the following:
The adjustment works on a separate test script that I extracted parts of the script out for testing. However when I deploy it to the real script, it doesnt work anymore. I then did a trial-error sequence and found that after certain 'additions' to the code, anything I add, such as a simple print "hello" statement, would result in the fcntl line not working. (The error outputted is Invalid Argument supplied).
Is it because the offset, len, l_whence are not defined correctly?
You shouldn't be using ioctl in perl. If your structure and C's disagree even slightly, then weird things can happen. If your structure and perl's completely agree, weird things can still happen. There may be memory alignment considerations and the like which rearrange or misalign the members from the arrangement you expected, only the C compiler's judgement should be trusted on that.
I seem to remember 'struct flock''s arrangement does seem to be different in OSX than in Linux, too. Something about one of the types involved not actually being an integer anymore.
Fortunately, perl has a built-in flock function so you don't need to call ioctl yourself. It's not even a module, it comes with standard perl.
Last edited by Corona688; 11-30-2011 at 03:29 PM..
fcntl, ioctl, same difference -- they're both raw system calls which need C data structures. You shouldn't be using them in perl, especially for programs you want to be portable. This might fail in different CPU architectures of the same Linux kernel, let alone a foreign OS.
perl's flock function exists because they're not the same everywhere.
thanks for your help. its interesting that i was able to get it to partially work but i guess it makes sense that the behavior is unpredictable at best. i never had an issue where adding debug print statements can break a script.
Hey guyz,
Is it possible to build user-mode linux kernel on MAC OSX?
Please I need a reply asap as I have an assignment that I need to do.
Thanks!
Adel (1 Reply)
Hi,
Unless I am missing some serious differences in Mac and linux in terms of C programming, I dont know why this would happen. Please take a look at the following piece of code fragment:
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