Getting PIDs which have files open / waiting for file write to complete

prell · 03-29-2005, 09:19 AM

I have a program that waits for new files in a directory. As soon as a new file is created, my program begins reading and processing it. Apparently, this reading can occur even as the file is being written, and may end before the write process is completed. Ideally, what I'd like to do is wait until the write is complete. I've tried opening the file for write access, which I assumed would wait until the other writing process closed the file, but that doesn't seem to be the case. Can this be done? Or, is there an easy way to figure out if someone (a process) has a file open for write access?

itsme86 · 03-29-2005, 09:25 AM

Do you control the process that's writing the files? If so, you may be able to use fcntl(). You didn't mention what language your program is written in, but this is for C/C++. You'd use it with this flag:

Code:

       F_SETLK
              The lock is set (when l_type is F_RDLCK or F_WRLCK)
              or cleared (when it is F_UNLCK).  If  the  lock  is
              held by someone else, this call returns -1 and sets
              errno to EACCES or EAGAIN.

prell · 03-29-2005, 09:39 AM

Oh yeah whoops, I'm sorry: I do not have control over the program(s) writing the files. However, it will be samba or scp or just cp, usually. My code is in C++.