lock file between C and php -

although title mentions file, doesn't have file. locking mechanism do.

here situation: have daemon process written in c, , web page in php. i'd have way of mutual locking under situation, c daemon lock file , php detects situation , tells client side system busy.

is there easy way of doing this?

thanks,

flock properly.

in php script, use non-blocking lock:

$fd = fopen('/var/run/lock.file', 'r+'); if (!flock($fd, lock_sh | lock_nb, $wouldblock) && $wouldblock) {     // buzy } 

the lock_nb flag make call non blocking. if file locked exclusively, return immediately. multiple pages allowed lock file @ same time.

you can release lock with

flock($fd, lock_un); 

in c daemon, use blocking , exclusive lock:

flock(fd, lock_ex); // wait until no page has locked file 

see php's flock() documentation , c's one