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?
Please help if you are familiar with Mac OSX. I downloaded OpenSSH for a newer version of SSH than what comes with OS 10.1. What a mistake! Now every time I try to make a connection to my remote server I get an message that ssh was built against version such and such and I have version such and... (2 Replies)
I finally broke down and decided to buy a new piece of hardware. I think I made the right decision when I chose an Apple iBook - OSX is incredible! I haven't used a Mac since System7.5, and 10.2 is just blowing me away!
Best of all, it's easy to use for people who are not used to Mac, but if I... (5 Replies)
I'm currently looking for an emulation program that would allow me to open and run osx app.s and programs on a windows xp based system.
if not is there a unix/linux/lindows program that may do the same? (3 Replies)
Hello,
I am trying to write a simple program with functions in the ncurses library, on a Mac running OSX 10.2.8, with the compiler and libraries that were included in the Dec 2002 Developer's tools release (the last one that runs on Jaguar, as far as I know). When I try to compile, I get... (2 Replies)
Hi,
I have installed bash 3.2 via darwin ports, however when I try and change the shell i.e. chsh -s /opt/local/bin/bash is says its a non-standard shell? but if i run ./bash i get a new bash prompt with version 3.2?
Thanks (3 Replies)
I've got this problem. My computers and external hard drives are converting many of my files to a Unix Executable File which has a grey terminal looking icon. I don't understand what is causing this to happen. It is happening to a large number of my image file of different formats and also... (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:
bool add_input_to_db(Cons *new_data) {
// Set the attributes of the lock
struct flock fl =... (3 Replies)
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)
Discussion started by: aje02
1 Replies
LEARN ABOUT PHP
flock
FLOCK(3) 1 FLOCK(3)flock - Portable advisory file lockingSYNOPSIS
bool flock (resource $handle, int $operation, [int &$wouldblock])
DESCRIPTION flock(3) allows you to perform a simple reader/writer model which can be used on virtually every platform (including most Unix derivatives
and even Windows).
On versions of PHP before 5.3.2, the lock is released also by fclose(3) (which is also called automatically when script finished).
PHP supports a portable way of locking complete files in an advisory way (which means all accessing programs have to use the same way of
locking or it will not work). By default, this function will block until the requested lock is acquired; this may be controlled with the
LOCK_NB option documented below.
PARAMETERS
o $handle
-A file system pointer resource that is typically created using fopen(3).
o $operation
-$operation is one of the following:
o LOCK_SH to acquire a shared lock (reader).
o LOCK_EX to acquire an exclusive lock (writer).
o LOCK_UN to release a lock (shared or exclusive).
It is also possible to add LOCK_NB as a bitmask to one of the above operations if you don't want flock(3) to block while locking.
o $wouldblock
- The optional third argument is set to 1 if the lock would block (EWOULDBLOCK errno condition).
RETURN VALUES
Returns TRUE on success or FALSE on failure.
CHANGELOG
+--------------+---------------------------------------------------+
| Version | |
| | |
| | Description |
| | |
+--------------+---------------------------------------------------+
|5.5.22, 5.6.6 | |
| | |
| | Added support for the $wouldblock parameter on |
| | Windows. |
| | |
| 5.3.2 | |
| | |
| | The automatic unlocking when the file's resource |
| | handle is closed was removed. Unlocking now |
| | always has to be done manually. |
| | |
+--------------+---------------------------------------------------+
EXAMPLES
Example #1
flock(3) example
<?php
$fp = fopen("/tmp/lock.txt", "r+");
if (flock($fp, LOCK_EX)) { // acquire an exclusive lock
ftruncate($fp, 0); // truncate file
fwrite($fp, "Write something here
");
fflush($fp); // flush output before releasing the lock
flock($fp, LOCK_UN); // release the lock
} else {
echo "Couldn't get the lock!";
}
fclose($fp);
?>
Example #2
flock(3) using the LOCK_NB option
<?php
$fp = fopen('/tmp/lock.txt', 'r+');
/* Activate the LOCK_NB option on an LOCK_EX operation */
if(!flock($fp, LOCK_EX | LOCK_NB)) {
echo 'Unable to obtain lock';
exit(-1);
}
/* ... */
fclose($fp);
?>
NOTES
Note
flock(3) uses mandatory locking instead of advisory locking on Windows. Mandatory locking is also supported on Linux and System V
based operating systems via the usual mechanism supported by the fcntl() system call: that is, if the file in question has the set-
gid permission bit set and the group execution bit cleared. On Linux, the file system will also need to be mounted with the mand
option for this to work.
Note
Because flock(3) requires a file pointer, you may have to use a special lock file to protect access to a file that you intend to
truncate by opening it in write mode (with a "w" or "w+" argument to fopen(3)).
Note
May only be used on file pointers returned by fopen(3) for local files, or file pointers pointing to userspace streams that imple-
ment the streamWrapper.stream_lock(3) method.
Warning
Assigning another value to $handle argument in subsequent code will release the lock.
Warning
On some operating systems flock(3) is implemented at the process level. When using a multithreaded server API like ISAPI you may
not be able to rely on flock(3) to protect files against other PHP scripts running in parallel threads of the same server instance!
flock(3) is not supported on antiquated filesystems like FAT and its derivates and will therefore always return FALSE under this
environments (this is especially true for Windows 98 users).
PHP Documentation Group FLOCK(3)