Linux常见定义记录

Figure 4.10 umask

Mask bit	Meaning
0400	user-read
0200	user-write
0100	user-execute
0040	group-read
0020	group-write
0010	group-execute
0004	other-read
0002	other-write
0001	other-execute

$ umask                        first print the current file mode creation mask
002
$ umask -S                     print the symbolic form
u=rwx,g=rwx,o=rx
$ umask 027                    change the file mode creation mask
$ umask -S                     print the symbolic form
u=rwx,g=rx,o=

//=================================================//

Figure 4.11. The mode constants forchmod functions, from <sys/stat.h>

mode	Description
S_ISUID	set-user-ID on execution
S_ISGID	set-group-ID on execution
S_ISVTX	saved-text (sticky bit)
S_IRWXU	read, write, and execute by user (owner)
S_IRUSR	read by user (owner)
S_IWUSR	write by user (owner)
S_IXUSR	execute by user (owner)
S_IRWXG	read, write, and execute by group
S_IRGRP	read by group
S_IWGRP	write by group
S_IXGRP	execute by group
S_IRWXO	read, write, and execute by other (world)
S_IROTH	read by other (world)
S_IWOTH	write by other (world)
S_IXOTH	execute by other (world)

S_IRWXO的全称是什么呢？哦，是这样啊  set-group-ID or a set-user-ID ，一看就明白了

S:                set

I:                 ID

RWX:         read,write,execute

O:               other

设定other这个项的file permission ID  是read , write,   execute。