????1??chmod
????????????????change the permissions mode of a file
??????????????·????/bin/chmod
?????????????????????
??????????chmod [{ugoa}{+-=}{rwx}] [???????]
????[???????] [???????]
????-R ??????
????????????????????????????
????*??????????“??????”????“root???”?????????????????????
????*u?????????g???????飬o?????????a????????
????*????????r(??)??4??w(д)??2??x(???)??1
????????chmod 755 /tmp/test  ???????????????rwxr-xr-x??

????*??ж?????????????”д???“?????????????
????2?? chown
????????????????change file ownership
??????????????·????/bin/chown
????????????????????
??????????chown [???] [???????]
?????????????????????????????????
???????????chown yonghu /tmp/test????????/tmp/test?????????yonghu??
????*???root????????????????????
????*?????????????????д???????
????3??chgrp
????????????????change file group ownership
??????????????·????/bin/chgrp
????????????????????
??????????chgrp [?????] [???????]
?????????????????????????????????
???????????chgrp yonghuzu /tmp/test????????/tmp/test?????????yonghuzu??
????4??umask
????????????????the user file-creation mask
??????????????·????Shell????????
????????????????????
??????????umask [-S]
????-S ??rwx?????????????????
??????????????????????????????????
????*???touch?????????????п???????????????????????п????????
????*?????? u=rwx??g=rx??o=rx????????????rw-r--r--
????*????????????????777?????????????????????
????*??????????????u=rwx??g=rx??o=r ??754????777-754=023??
????*???????umask 023