函数原型：
#include <sys/stat.h>
int mkdir(const char *path, mode_t mode);
参数：
path是目录名
mode是目录权限
返回值：
返回0 表示成功， 返回 -1表示错误，并且会设置errno值。
mode模式位：
mode 表示新目录的权限，可以取以下值：
S_IRUSR
S_IREAD
S_IWUSR
S_IWRITE
S_IXUSR
S_IEXEC
S_IRWXU
This is equivalent to (S_IRUSR | S_IWUSR | S_IXUSR).
S_IRGRP
Read permission bit for the group owner of the file. Usually 040.
S_IWGRP
Write permission bit for the group owner of the file. Usually 020.
S_IXGRP
Execute or search permission bit for the group owner of the file. Usually 010.
S_IRWXG
This is equivalent to (S_IRGRP | S_IWGRP | S_IXGRP).
S_IROTH
Read permission bit for other users. Usually 04.
S_IWOTH
Write permission bit for other users. Usually 02.
S_IXOTH
Execute or search permission bit for other users. Usually 01.
S_IRWXO
This is equivalent to (S_IROTH | S_IWOTH | S_IXOTH).
S_ISUID
This is the set-user-ID on execute bit, usually 04000. See How Change Persona.
S_ISGID
This is the set-group-ID on execute bit, usually 02000. See How Change Persona.
S_ISVTX
This is the sticky bit, usually 01000.
例子：
#include <sys/types.h> #include <sys/stat.h>
int status;
status = mkdir("/home/newdir", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
这样就创建了一个newdir目录，权限通过ls -al 查看为
drwxr-xr-x
跟用linux命令mkdir创建的目录权限位一致。