gpm -D is a option which makes gpm emit some debug info to stdout. I am using it for many years. In recent version it has been broken.

When stdout is a tty, gpm does print some messages:

# gpm -D -2 -m /dev/not_exist -t bare
*** info [startup.c(95)]: Started gpm successfully. Entered daemon mode.

If I want to process them with some program:

# gpm -D -2 -m /dev/not_exist -t bare | cat

No output.

Same happens if I redirect output to a file:

# gpm -D -2 -m /dev/not_exist -t bare >FILE
# ls -l FILE
-rw-r--r-- 1 root root 0 2008-11-27 14:57 FILE

strace reveals that it seems to be done intentionally. gpm tests the type of stdout:

fstat(1, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0

and if it is not a tty, it doenst print anything. What is the rationale of such a strange behavior?

Another bug is that gpm closes stdin/out/err and loses all further messages (writes them to closed fds), but I was told it is already fixed in newer version.