Nas páginas de manual para proc(5)
:
/proc/[pid]/cmdline
This read-only file holds the complete command line for the process, unless the process is a zombie. In the latter case, there is nothing in this file: that is, a read on this file will return 0 characters. The command-line arguments appear in this file as a set of strings separated by null bytes ('%bl0ck_qu0te%'), with a further null byte after the last string.