On Wed, Jan 08, 2003 at 06:33:12AM +0000, Anticipating a Reply wrote: > I was reading Linux Device Drivers , by > A.Rubini and found the below lines on page 71 > near the end . > > " The only real operation performed on the > device is truncating it to a length of zero when > the device is opened for writing. This is > performed because, by design, overwriting a pscull > device with a shorter file results in a shorter > device data area. This is similar to the way > opening a regular file for writing truncates it to > zero length. The operation does nothing if the > device is opened for reading. " > > As said above in the last lines , I tried > the open system call on a regular file ,with > O_WRONLY option , without doing any further > operations . I was expecting the regular file to > truncate to zero after the open call as said above, > but I found that the regular file is > intact . > > Can anybody please explain ? > Or maybe I have not understood the above lines > properly . The author of the above did not state wether he means libc's and systems's terminology. As for system, file is only truncated if O_TRUNC flag is given to open syscall. However the libc means O_WRONLY|O_TRUNC by write and O_WRONLY is called append there. Author of the above probably ment whe libc's write and if you call fopen(..., "w"), the file will be truncated. ------------------------------------------------------------------------------- Jan 'Bulb' Hudec <bulb@ucw.cz> -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
