Referring to this question, and particularly to the output of ipcs -s -i 65536, what is the meaning of pid 0?For example, in my system:# ipcs -s------ Semaphore Arrays --------key        semid      owner      perms      nsems     0x02004393 5013511    user_one   744        1         0x53020010 753673     user_two   744        1         # ipcs -s -i 5013511Semaphore Array semid=5013511uid=702  gid=501     cuid=702    cgid=501mode=0744, access_perms=0744nsems = 1otime = Not set                   ctime = Mon Sep  5 17:35:42 2016  semnum     value      ncount     zcount     pid       0          0          0          0          0         
Meaning of pid 0 in ipcs -s -i 
linux