fcntl(2)    http://man.cx/fcntl(2)
flock(2)    http://man.cx/flock(2)
su(1)       http://man.cx/su(1)
newgrp(1)   http://man.cx/newgrp(1)
setpgrp(1)  http://man.cx/setpgrp(1)
nohup(1)    http://man.cx/nohup(1)
nice(1)     http://man.cx/nice(1)
