Re: Practical flock() implementation

Hello CC, On 23-Jun-01 17:25:54, you wrote: >I'm having trouble understanding the docs and annotations on flock(). I've >got a script that needs to overwrite a data file's contents without letting >Instance B of that script truncate the data file while Instance A is still >writing new content to it. How do other people do this? It seems to me Let me guess: you are developing a cache system, right? :-) >that if I fopen() in "w" or "w+" mode, then the file will be truncated >before it can be determined whether there's a lock already in effect or the >current instance can acquire a lock; but flock() requires a filepointer >argument, so don't I *have* to fopen the file before going to flock()? Or >should I fopen first in "r" mode, acquire the lock, then re-open in "w" >mode, counting on the lock to stay in effect even though it's a different >file pointer? I know that second solution works, but I don't know about its portability. >I'd also be grateful if someone could clarify the difference between >blocking and locking (i.e. "If you don't want flock() to block while >locking, add LOCK_NB (4 prior to PHP 4.0.1) to operation."). If you don't want to wait in case it is not possible to obtain the lock right away, using non-blocking locks. Regards, Manuel Lemos Web Programming Components using PHP Classes. Look at: http://phpclasses.UpperDesign.com/?user=mlemos@acm.org -- E-mail: mlemos@acm.org URL: http://www.mlemos.e-na.net/ PGP key: http://www.mlemos.e-na.net/ManuelLemos.pgp --