On SunOS there is pargs command that prints the command line arguments passed to the running process.
pargs
Is there is any similar command on other Unix env
Another variant of printing /proc/PID/cmdline with spaces in Linux is:
/proc/PID/cmdline
cat -v /proc/PID/cmdline | sed 's/\^@/\ /g' && echo
In this way cat prints NULL characters as ^@ and then you replace them with a space using sed; echo prints a newline.
cat
^@
sed
echo