Linux chmod、fchmod函数

chmod、fchmod

头文件

#include

函数原型

int chmod(const char *path, mode_t mode);
int fchmod(int fd, mode_t mode);

功能

chmod函数在指定的文件上进行操作，改变现有文件的访问权限。fchmod对已打开的文件进行操作。 修改时，进程的有效用户ID必须等于文件的所有者ID，或是root运行的此进程。

参数

mode常量

       S_ISUID  (04000)  set-user-ID  (set  process  effective  user  ID   on
                         execve(2))//执行时设置用户ID

       S_ISGID  (02000)  set-group-ID  (set  process  effective  group  ID on
                         execve(2);  mandatory  locking,  as   described   in
                         fcntl(2); take a new file's group from parent direc-
                         tory, as described in chown(2) and mkdir(2))//执行时设置组ID

       S_ISVTX  (01000)  sticky bit (restricted deletion flag,  as  described
                         in unlink(2))//保存正文(粘住位)

       S_IRUSR  (00400)  read by owner//用户(所有者)读

       S_IWUSR  (00200)  write by owner//用户(所有者)写

       S_IXUSR  (00100)  execute/search by owner ("search" applies for direc-
                         tories, and means that entries within the  directory
                         can be accessed)//用户(所有者)执行


       S_IRGRP  (00040)  read by group//组读
       S_IWGRP  (00020)  write by group//组写
       S_IXGRP  (00010)  execute/search by group//组执行

       S_IROTH  (00004)  read by others//其他读

       S_IWOTH  (00002)  write by others//其他写

       S_IXOTH  (00001)  execute/search by others//其他执行
       S_IRWXU  (UNIX)   //用户读写执行
       S_IRWXG  (UNIX)   //组读写执行
       S_IRWXO  (UNIX)   //其他读写执行

unix环境高级编程的例子

#include 
#include 
#include 
#include 

int main(int argc, char * argv[])
{
	struct stat statbuf;

	if(stat("foo", &statbuf) <  0)
	{
		printf("stat error for foo\n");
	}	

	if(chmod("foo", (statbuf.st_mode & ~S_IXGRP) | S_ISGID) < 0)
	{
		printf("chmod error for foo\n");
	}

	if(chmod("bar", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) < 0)
	{
		printf("chmod error for bar\n");
	}
	exit(0);
}