chown, fchown, lchown - 改變文件的所有權

內容簡介

#include <sys/types.h>
#include <unistd.h>

int chown(const char **path*, uid_t owner**, gid_t** group**);** int fchown(int fd**, uid_t** owner**, gid_t** group**);** int lchown(const char **path*, uid_t owner**, gid_t** group**);**

描述

These system calls change the owner and group of the file specified by path or by fd. Only a privileged process (Linux: one with the CAP_CHOWN capability) may change the owner of a file. The owner of a file may change the group of the file to any group of which that owner is a member. A privileged process (Linux: with CAP_CHOWN) may change the group arbitrarily.

If the owner or group is specified as -1, then that ID is not changed. When the owner or group of an executable file are changed by a non-superuser, the S_ISUID and S_ISGID mode bits are cleared. POSIX does not specify whether this also should happen when root does the chown(); the Linux behaviour depends on the kernel version. In case of a non-group-executable file (with clear S_IXGRP bit) the S_ISGID bit indicates mandatory locking, and is not cleared by a chown().

返回值

成功，則返回0。上的錯誤，則返回-1，errno設置爲合適。

錯誤

根據文件系統上的，其他錯誤，也可以返回 chown() 更一般的錯誤在下面列出。 

Error Code

描述

EACCES

Search permission is denied on a component of the path prefix. (See also path_resolution(2).)

EFAULT

path points outside your accessible address space.

ELOOP

Too many symbolic links were encountered in resolving path.

ENAMETOOLONG

path is too long.

ENOENT

The file does not exist.

ENOMEM

Insufficient kernel memory was available.

ENOTDIR

A component of the path prefix is not a directory.

EPERM

The calling process did not have the required permissions (see above) to change owner and/or group.

EROFS

The named file resides on a read-only file system.

The general errors for fchown() are listed below:

EBADF

The descriptor is not valid.

EIO

A low-level I/O error occurred while modifying the inode.

ENOENT

See above.

EPERM

See above.

EROFS

See above.

注意

In versions of Linux prior to 2.1.81 (and distinct from 2.1.46), chown() did not follow symbolic links. Since Linux 2.1.81, chown() does follow symbolic links, and there is a new system call lchown() that does not follow symbolic links. Since Linux 2.1.86, this new call (that has the same semantics as the old chown()) has got the same syscall number, and chown() got the newly introduced number.

The prototype for fchown() is only available if _BSD_SOURCE is defined.

遵循於

4.4BSD, SVr4, POSIX.1-2001. The 4.4BSD version can only be used by the superuser (that is, ordinary users cannot give away files).

限制

The chown() semantics are deliberately violated on NFS file systems which have UID mapping enabled. Additionally, the semantics of all system calls which access the file contents are violated, because chown() may cause immediate access revocation on already open files. Client side caching may lead to a delay between the time where ownership have been changed to allow access for a user and the time where the file can actually be accessed by the user on other clients.

另請參閱

• chmod (2)

• fchownat (2)

• flock (2)

• path_resolution (2)