linux c语言 rename的用法-rename() does not work across different mount points, even if the same file system is mounted on both

最近在一个项目上执行文件的搬移功能时发现总是失败，临时录像文件存放于emmc的/tmp/目录下，当录像完成时候则调用rename企图将此文件搬到/mnt/sdcard/mmcblk1p1/（这是外置的sd卡）上面，但是每次执行rename的时候都返回失败了。

man 2  rename解释如下：

 1 RENAME(2)                                                           Linux Programmer's Manual                                                          RENAME(2)
 2
 3 NAME
 4        rename - change the name or location of a file
 5
 6 SYNOPSIS
 7        #include <stdio.h>
 8
 9        int rename(const char *oldpath, const char *newpath);
10
11 DESCRIPTION
12        rename()  renames  a  file, moving it between directories if required.  Any other hard links to the file (as created using link(2)) are unaffected.  Open
13        file descriptors for oldpath are also unaffected.
14
15        If newpath already exists it will be atomically replaced (subject to a few conditions; see ERRORS below), so that there is  no  point  at  which  another
16        process attempting to access newpath will find it missing.
17
18        If oldpath and newpath are existing hard links referring to the same file, then rename() does nothing, and returns a success status.
19
20        If newpath exists but the operation fails for some reason rename() guarantees to leave an instance of newpath in place.
21
22        oldpath can specify a directory.  In this case, newpath must either not exist, or it must specify an empty directory.
23
24        However, when overwriting there will probably be a window in which both oldpath and newpath refer to the file being renamed.
25
26        If oldpath refers to a symbolic link the link is renamed; if newpath refers to a symbolic link the link will be overwritten.
27
28 RETURN VALUE
29        On success, zero is returned.  On error, -1 is returned, and errno is set appropriately.
30
31 ERRORS
32        EACCES Write permission is denied for the directory containing oldpath or newpath, or, search permission is denied for one of the directories in the path
33               prefix of oldpath or newpath, or oldpath is a directory and does not allow write permission (needed to update the ..  entry).  (See also path_res‐
34               olution(7).)
35
36        EBUSY  The rename fails because oldpath or newpath is a directory that is in use by some process (perhaps as current working directory, or as root direc‐
37               tory, or because it was open for reading) or is in use by the system (for example as mount point), while  the  system  considers  this  an  error.
38               (Note  that  there is no requirement to return EBUSY in such cases—there is nothing wrong with doing the rename anyway—but it is allowed to return
39               EBUSY if the system cannot otherwise handle such situations.)

EFAULT oldpath or newpath points outside your accessible address space.

EINVAL The new pathname contained a path prefix of the old, or, more generally, an attempt was made to make a directory a subdirectory of itself.

EISDIR newpath is an existing directory, but oldpath is not a directory.

ELOOP Too many symbolic links were encountered in resolving oldpath or newpath.

EMLINK oldpath already has the maximum number of links to it, or it was a directory and the directory containing newpath has the maximum number of links.

ENAMETOOLONG
oldpath or newpath was too long.

ENOENT The link named by oldpath does not exist; or, a directory component in newpath does not exist; or, oldpath or newpath is an empty string.

ENOMEM Insufficient kernel memory was available.

ENOSPC The device containing the file has no room for the new directory entry.

ENOTDIR
A component used as a directory in oldpath or newpath is not, in fact, a directory. Or, oldpath is a directory, and newpath exists but is not a
directory.

ENOTEMPTY or EEXIST
newpath is a nonempty directory, that is, contains entries other than "." and "..".

EPERM or EACCES
The directory containing oldpath has the sticky bit (S_ISVTX) set and the process's effective user ID is neither the user ID of the file to be
deleted nor that of the directory containing it, and the process is not privileged (Linux: does not have the CAP_FOWNER capability); or newpath is
an existing file and the directory containing it has the sticky bit set and the process's effective user ID is neither the user ID of the file to
be replaced nor that of the directory containing it, and the process is not privileged (Linux: does not have the CAP_FOWNER capability); or the
file system containing pathname does not support renaming of the type requested.

EROFS The file is on a read-only file system.

EXDEV oldpath and newpath are not on the same mounted file system. (Linux permits a file system to be mounted at multiple points, but rename() does not
work across different mount points, even if the same file system is mounted on both.)

EXDEV oldpath and newpath are not on the same mounted file system. (Linux permits a file system to be mounted at multiple points, but rename() does not
work across different mount points, even if the same file system is mounted on both.)

CONFORMING TO
4.3BSD, C89, C99, POSIX.1-2001.

BUGS
On NFS file systems, you can not assume that if the operation failed the file was not renamed. If the server does the rename operation and then crashes,
the retransmitted RPC which will be processed when the server is up again causes a failure. The application is expected to deal with this. See link(2)
for a similar problem.

SEE ALSO
mv(1), chmod(2), link(2), renameat(2), symlink(2), unlink(2), path_resolution(7), symlink(7)

COLOPHON
This page is part of release 3.35 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at
http://man7.org/linux/man-pages/.

Linux 2009-03-30

注意看最后一个ERRORS类型

EXDEV oldpath and newpath are not on the same mounted file system. (Linux permits a file system to be mounted at multiple points, but rename() does not
work across different mount points, even if the same file system is mounted on both.)

回想以前使用rename的时候没有失败过，因为都是在一个磁盘上操作，现在是在两个磁盘上不同的挂载点。这正是rename失败的原因。

所以最后之只能放弃这个方法，采用system 的mv或者同时读写两个文件的方法测试后发现没多大差别效率都比较低。