Process Identification !!

[dannymm]

Hi Guys,

Is there any way to check if a program is already instantiated, i,e if i am running program A and if i want to run another instance(assume another user) ... i want to make sure that another instance of program A is not running ..... and i want the second user to wait until the first instance of the program exits.

i think i should be checking the internal process id of the php script and verify it's status. But i am not sure if i can do it .....

Any suggestions ...

Thanks in Advance ..
Danny !!

[[deleted]]

Try a PID file.
When the PHP script starts, make it write an empty file in a pre-defined location.
When the script exists, make it remove the file.

When another script starts, make it check for that file. If the file already exists, another script must be running.

You can make PHP wait for the script to finish, but that will sooner or later cause your server to have 400 processes waiting for eachother.

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[dannymm]

what if the user presses the stop button ... will i be able to delete the pid file in the above case ...

The program which i am talking about usually runs for quite a long time (5 minutes to 30 minutes depending on file size ...)

I am parsing some XML files from a particular directory ... my intention is to avoid two instances of the program accessing the directory at the same time ...