attr_get (3) - Linux Manuals

attr_get: get the value of a user attribute of a filesystem object

NAME

attr_get, attr_getf - get the value of a user attribute of a filesystem object

C SYNOPSIS

#include <attr/attributes.h>

int attr_get (const char *path, const char *attrname, 
              char *attrvalue, int *valuelength, int flags);

int attr_getf (int fd, const char *attrname, 
               char *attrvalue, int *valuelength, int flags);
[

DESCRIPTION

] The attr_get and attr_getf functions provide a way to retrieve the value of an attribute.

Path points to a path name for a filesystem object, and fd refers to the file descriptor associated with a file. If the attribute attrname exists, the value associated with it will be copied into the attrvalue buffer. The valuelength argument is an input/output argument that on the call to attr_get should contain the maximum size of attribute value the process is willing to accept. On return, the valuelength will have been modified to show the actual size of the attribute value returned. The flags argument can contain the following symbols bitwise OR'ed together:

ATTR_ROOT

Look for attrname in the root address space, not in the user address space. (limited to use by super-user only)

ATTR_DONTFOLLOW

Do not follow symbolic links when resolving a path on an attr_get function call. The default is to follow symbolic links.

attr_get will fail if one or more of the following are true:

[ENOATTR]

The attribute name given is not associated with the indicated filesystem object.

[E2BIG]

The value of the given attribute is too large to fit into the buffer. The integer that the valuelength argument points to has been modified to show the actual number of bytes that would be required to store the value of that attribute.

[ENOENT]

The named file does not exist.

[EPERM]

The effective user ID does not match the owner of the file and the effective user ID is not super-user.

[ENOTDIR]

A component of the path prefix is not a directory.

[EACCES]

Search permission is denied on a component of the path prefix.

[EINVAL]

A bit was set in the flag argument that is not defined for this system call.

[EFAULT]

Path, attrname, attrvalue, or valuelength points outside the allocated address space of the process.

[ELOOP]

A path name lookup involved too many symbolic links.

[ENAMETOOLONG]

The length of path exceeds {MAXPATHLEN}, or a pathname component is longer than {MAXNAMELEN}.

attr_getf will fail if:

[ENOATTR]

The attribute name given is not associated with the indicated filesystem object.

[E2BIG]

The value of the given attribute is too large to fit into the buffer. The integer that the valuelength argument points to has been modified to show the actual numnber of bytes that would be required to store the value of that attribute.

[EINVAL]

A bit was set in the flag argument that is not defined for this system call, or fd refers to a socket, not a file.

[EFAULT]

Attrname, attrvalue, or valuelength points outside the allocated address space of the process.

[EBADF]

Fd does not refer to a valid descriptor.

DIAGNOSTICS

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.