Example. fopen(“”,”w+”); // exclusive lock if (flock($file, LOCK_EX)) { fwrite($file,”Write something”); // release lock flock($file,LOCK_UN); } else. flock. (PHP 4, PHP 5, PHP 7). flock — Portable advisory file locking A file system pointer resource that is typically created using fopen(). operation. operation is. $fh = fopen(”,’a’) or die($php_errormsg); flock($fh,LOCK_EX) or The file locking flock() provides is called advisory file locking because flock().

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Stack Overflow works best with JavaScript enabled. 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 clock or it will not work. From the Linux man page of open: Maybe you can give me some credit by leaving in the author comment, but it is not required.

Prevent multiple PHP scripts at the same time. If while the first script is sleeping you launch the second script, it will wait “block” on the flock call and wait for the first script to finish.

The automatic unlocking when the file’s resource handle is closed was removed. If it exists, it is neither truncated as opposed to ‘w’nor the call to this function fails as is the case with ‘x’. The list of supported protocols can be found in Supported Protocols and Wrappers.

Finally, how to prevent multiple PHP scripts to run at the same fpock In the end, this was a lot of learning in one afternoon, and clock finished well. This is an addendum to ibetyouare at home dot com’s note about Apache directory permissions. You may use to suppress this warning.


It looks like the second one tlock needed so the server won’t interpret the path as relative to blossom’s home on townsville. If you wish to implement your own lock simply, I suggest Rob’s answer of using flock.

Locking with flock doesn’t work in all circumstances, such as on some NFS implementations. On a Windows webserver, when using fopen with a file path stored in a variable, PHP will return an error if the variable isn’t encoded in ASCII, which may be the case if the file fppn path is retrieved from a database.

PHP: fopen – Manual

I waited a bit, expecting the port to be released with some flokc, but that was wrong. Even though it is a core and —enable extension, this is not available by default. Works with SSL-secured hosts.

I wonder if there is any way to lock and unlock a file in Linux when I open a file using fopen not open? Edit Report a Bug. Too much compilation for Docker The next snag I hit with this is when creating the Docker file. PHP offers flockin the standard functions, fo;n implements a locking mechanism at the file level.

Portable advisory file locking

The lock was kept alive until apache recycled those processes. The code is here: By default, flock blocks until it can obtain a lock.

I tried append mode and it errors out so does not seem to be dangerous. From the Solaris man page for flock: The supplied documentation is vague, ambiguous and lacking, and the user comments contain erroneous information!

Mandatory locking is also supported on Linux and System V based operating systems via the usual mechanism supported by the fcntl system call: In case of a crash or interruption, this brilliant system will be left with a lot of garbage, including the lock directory.


You may want to issue a touch after writing and closing the file which update its modification time. This is some code to work around the close and re-open of stdin. Checking uploaded files Jump to: On some operating systems flock flkck implemented at the process level. 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. Calling flock will return true if the file lock was retrieved successfully, or false if it failed.

Had to do this flocj for a shoutcast server, which only delivered the HTML-file if the user-agent was given.

gopn Also, some old file systems are not supported. Fatal Protocol Error” when you reach the end of the data. Something was not releasing the process. If a lock cannot be obtained because another application has a lock, the script waits at the flock call for the lock to be released, then locks it itself and continues.

This just bit me. Changelog Version Description 5.

Locking files with flock()

While opening a file with multibyte data Ex: Parameters filename If filename is of the form “scheme: It uses an IP 0. For instance, try concurrently running two instances of the following script via the CLI. If you are getting message “Warning: