Experimental Physics and
Industrial Control System

Noboru Yamamoto <[email protected]> · Wed, 26 Jan 2000 19:18:53 +0900

Dear All,

I have implemented a Python function  ca.add_fd_registration() in our
CaPython software.
The following is a sample Python script which uses 
ca.add_fd_registration() to register
fd registration function.

#===========

def myFdRegister(arg, fd, condition):
    if condition:
        sys.stderr.write( "registering fd:%d msg:%s\n"%(fd,arg))
        sys.stderr.flush()
    else:
        sys.stderr.write("deleting fd:%d\n"%fd)
        sys.stderr.flush()

import ca
ca.add_fd_registration(myFdRegister, "Hello World")

print ca.Get("CO_IOC:COCCC:CLOCK")

#===========

ca.add_fd_registration()  corresponds to the ca_add_fd_registration()
function in CA library. A registered function( myFdRegister() in the
above example) will called every time CA libaray opens or closes a file descriptor.
As in the case of ca_add_fd_registration(), ca.add_fd_registration()
should be called before any access to the channel. 

_ca.c uses Tk_CreateFileHandler()/Tk_DeleteFileHandler() in the default
fd_registration function. So most user may not need this function.

Noboru Yamamoto
KEKB control group
KEK, JAPAN

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System