Very Computer

Can anyone direct me how fcntl call works in locking a region of a file ?

I tried locking a file with this call,

fcntl(fd,F_SETLK,&lk);  

where lk is a struct of type flock (defined in fcntl.h). The structures
elements were set to ,

lk.l_type = F_WRLCK; lk.l_whence = SEEK_SET; lk.l_start = 0;
  lk.l_len = 0;

After locking the file opened by fd, I had a sleep call so that I can
invoke an another process to open the same file and write some junk
data.

The write from the other process (on the same file) SUCCEEDED !!

- Any help how locking needs to be done !!

-Thanks Bye

Quote:>After locking the file opened by fd, I had a sleep call so that I can
>invoke an another process to open the same file and write some junk
>data.
>The write from the other process (on the same file) SUCCEEDED !!

: Can anyone direct me how fcntl call works in locking a region of a file ?

: After locking the file opened by fd, I had a sleep call so that I can
: invoke an another process to open the same file and write some junk
: data.

: The write from the other process (on the same file) SUCCEEDED !!

The lock that you obtained does not prevent other processes from
-writing- to the file, it prevents other processes from -locking-
the region that you locked.  What you want to do is lock the region
of interest (or the whole file as in your example), write to the file,
and then unlock it.  Do this in -all-processes involved, not just the
first one.

--
Clarence Gardner
King of All He Surveys (now where'd I put my transit?)