Polished messages, comments and description of DDLP-A

Thomas Schmitt 16 years ago
parent fd5b681bc6
commit 256139c9d6
  1. 38
  2. 10
  3. 3

@ -148,6 +148,44 @@ With hdc, of course, things are trivial
ddlpa: opened /dev/hdc
slept 1 seconds of 1
Ted Ts'o provided program open-cd-excl which allows to explore open(2) on
device files with combinations of read-write, O_EXCL, and fcntl().
(This does not mean that Ted endorsed our project yet. He helps exploring.)
Friendly in the sense of DDLP-A would be any run which uses at least one of
the options -e (i.e. O_EXCL) or -f (i.e. F_SETLK).
The code is available under GPL at
To be compiled by
cc -g -Wall -o open-cd-excl open-cd-excl.c
-e : open O_EXCL
-f : aquire lock by fcntl(F_SETLK) after sucessful open
-i : do not wait in case of success but exit 0 immediately
-r : open O_RDONLY , with -f use F_RDLCK
-w : open O_RDWR , with -f use F_WRLCK
plus the path of the devce file to open.
Friendly Programs would use gestures like:
./open-cd-excl -e -r /dev/sr0
./open-cd-excl -e -w /dev/sg1
./open-cd-excl -e -w /dev/black-drive
./open-cd-excl -f -r /dev/sg1
./open-cd-excl -e -f -w /dev/sr0
Ignorant programs would use:
./open-cd-excl -r /dev/sr0
./open-cd-excl -w /dev/sg1
./open-cd-excl -f -w /dev/black-drive
where "/dev/black-drive" is _not_ a symbolic link to
any of /dev/sr* /dev/scd* /dev/sg*, but has an own inode.
Prone to failure without further reason is:
./open-cd-excl -e -r /dev/sg1

@ -11,8 +11,8 @@
-DDDLPA_C_STANDALONE -o ddlpa ddlpa.c
The system macros are needed for 8-bit off_t and for open flag O_LARGEFILE
which are not absolutely necessary but explicitely take into respect that
The system macros enable 64-bit off_t and open(2) flag O_LARGEFILE, which
are not absolutely necessary but explicitely take into respect that
our devices can offer more than 2 GB of addressable data.
Run test program:
@ -42,6 +42,12 @@
static int ddlpa_debug_mode = 1;
/* #define _GNU_SOURCE or _LARGEFILE64_SOURCE to get real O_LARGEFILE */
#define O_LARGEFILE 0
/* ----------------------- private -------------------- */

@ -52,7 +52,7 @@ int main(int argc, char **argv)
progname = argv[0];
/* ts A70417: added -w and -r */
/* ts A70417: added -w , -r , -i */
while ((c = getopt (argc, argv, "feirw")) != EOF) {
switch (c) {
case 'e':
@ -119,6 +119,7 @@ int main(int argc, char **argv)
printf("Trying to grab fcntl lock...\n");
if (fcntl(fd, F_SETLKW, &fl) < 0) {
perror("fcntl: F_SETLKW: ");