> jc807j 2668 1 0 08:59 tty0 00:00:00 xterm -e ssh server
80x72+285+0 -e ssh server
> jc807j 3004 1 0 08:59 tty0 00:00:00 xterm -e ssh server
> 80x72-8+0 -e ssh server
> jc807j 2928 5852 0 09:12 ? 00:00:00 xterm 20000 +tb
> The actual command lines for the 3 xterm processes are:
> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72+285+0 -e ssh server
> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72-8+0 -e ssh server
> C:\cygwin\bin\xterm.exe -sl 20000 +tb
xterm calls XrmParseCommand() that
"parses an (argc, argv) pair according to the specified option table ... and
modifies the (argc, argv) pair to remove all recognized options."
Therefore
"-sl 20000 +tb -geometry 80x72+285+0"
is properly removed
and "-e ssh server" is moved to __argv[1 .. 3].
Then __argv[4] (respectively __argv[1] for the shorter command) is assigned
null pointer
which results in the second "\0" in the od-output below.
HOWEVER:
Either XrmParseCommand() does not update argc
or the change does not propagate (how would that be possible?) to __argc.
Therefore the command lines appear corrupted this particular way.
/proc/*/cmdline uses a copy of __argc named __argc_safe
which is hardly to be updated anyway.
" for (int i = 0; i < __argc_safe; i++) "
Funny enough, /proc/self/cmdline is likely to contain shortened version of
cmdline:
" for (char **a = __argv; *a; a++) "
[ pinfo.cc from cygwin 1.7.9-1 ]
> I have verified that the "/proc/*/cmdline" is the source of the
> corrupted information. "cmdline" from PID 2928 is:
>
> jc807j@~>od -c /proc/2928/cmdline
> 0000000 x t e r m \0 \0 2 0 0 0 0 \0 + t b
> 0000020 \0
> 0000021
----
What does xterm on different platforms ?
While concept of modifying own cmdline (In fact, __argv[0]) is used very
often to signal the process state down to the user,
I was never thinking of modifying argc:
main (int argc, char **argv)
:-)
JK
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