Re: [Vala] Checking file locks in Vala

[David Ma <dm10005 yahoo com>]

David Ma <dm10005    > writes:

> How do you check whether a file is locked in Vala? 
> However, this function needs to use the struct 'flock' as the third argument 
> passed to fcntl, but this struct doesn't exist in the posix.vapi file (at 
least, 
> I can't see it in there, or in Valadoc).

I put the following into the posix.vapi file, and now it's working. Therefore, 
there seems to currently be an omission in the posix.vapi.


[CCode (cheader_filename = "fcntl.h", cname = "struct flock")]
public struct Flock {
        public int  l_type;
        public int  l_whence;
        public off_t  l_start;
        public off_t  l_len;
        public pid_t  l_pid;
}



For the record, here is the lock-checking code (in case it might be useful to 
someone else):


public bool is_dpkg_locked() {
        
        string lock_file_name = "/var/lib/dpkg/lock";
        int fd = Posix.open (lock_file_name, Posix.O_RDWR); 
        if (fd == -1) {
          print ("There was an error opening the file '"  
            + lock_file_name + " (Error number "  
            + Posix.errno.to_string() + ")\n");
          return true;
        }
                
        // Try to get a lock
        Posix.Flock fl = Posix.Flock();
        fl.l_type = Posix.F_WRLCK;
        fl.l_whence = Posix.SEEK_SET;
        fl.l_start = 100;
        fl.l_len = 0;
                
        int fcntl_return = Posix.fcntl (fd, Posix.F_SETLK, fl);
        if (fcntl_return == -1) 
                return true;
                
        // Release the lock again
        fl.l_type = Posix.F_UNLCK;
        fl.l_whence = Posix.SEEK_SET;
        fl.l_start = 100;
        fl.l_len = 0;
        fcntl_return = Posix.fcntl (fd, Posix.F_SETLK, fl);

        return false;
}