file-locking

Suppose there are 2 processes P1 and P2, and they access a shared file Foo.txt . Suppose P2 is reading from Foo.txt . I don't want P1 to write to Foo.txt while P2 is reading it. So I thought I could make P1 write to Foo.tmp and as a last step, rename Foo.tmp to Foo.txt . My programming language is Java So my question is, would this ensure that P2 reads the correct data from Foo.txt ? Would the rename operation be committed once P2 completes reading the file? EDIT I tried to recreate this scenario as follows: My P1 code is something like this: File tempFile = new File(path1); File realFile =

script1.php <?php session_start(); sleep(10); script2.php <?php session_start(); I run script1.php in the browser and immediately after script2.php in another browser window. session_start() in script2.php can't execute until script1.php is not finished executing. Why it happened and how to make php scripts run in parallel? Try <?php session_start(); session_write_close(); sleep(10); Related: Thoughts on PHP sessions 来源： https://stackoverflow.com/questions/6618026/how-to-make-php-scripts-run-in-parallel

I intend to perform opening for reading a single file from many threads using std::ifstream. My concern is if std::ifstream is thread-safe & lock-free? More details: I use g++ 4.4 on Ubuntu & Windows XP, 4.0 on Leopard. Each thread creates its own instance of std::ifstream Thanks in advance! That is implementation defined. Standard C++ says absolutely nothing about threading, and therefore any assumptions about threads inherently invoke unspecified or implementation defined behavior. We need the platform you are using to be more specific, but it's probably unreasonable to assume ifstream is

In PHP, how can I test if a file has already been locked with flock ? For example, if another running script has called the following: $fp = fopen('thefile.txt', 'w'); flock($fp, LOCK_EX); Prateek if (!flock($fp, LOCK_EX|LOCK_NB, $wouldblock)) { if ($wouldblock) { // another process holds the lock } else { // couldn't lock for another reason, e.g. no such file } } else { // lock obtained } As described in the docs , use LOCK_NB to make a non-blocking attempt to obtain the lock, and on failure check the $wouldblock argument to see if something else holds the lock. Check it like this: if (!flock

I have a process that will be called rather frequently from cron to read a file that has certain move related commands in it. My process needs to read and write to this data file - and keep it locked to prevent other processes from touching it during this time. A completely separate process can be executed by a user to (potential) write/append to this same data file. I want these two processes to play nice and only access the file one at a time. The nio FileLock seemed to be what I needed (short of writing my own semaphore type files), but I'm having trouble locking it for reading. I can lock

This question already has an answer here: Unlock Files for deletion 2 answers I want my application to clean all the temp files it used, the problem is that not all the temp files are under my control, so I just want to "brutally" unlock them in order to delete them programatically. Take a look at this article. I think that you'll struggle to do this in C# natively, even using interop, but writing a C++/CLI wrapper assembly may be a good compromise. Note also that the user needs to have the SE_DEBUG privilege for this to work. I've struggled with this as well, and ended up just shelling out to