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GETXATTR

Linux Programmer's Manual (2)
2014-04-06
 

NAME

getxattr, lgetxattr, fgetxattr - retrieve an extended attribute value  

SYNOPSIS

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

ssize_t getxattr(const char *path, const char *name,
                 void *value, size_t size);
ssize_t lgetxattr(const char *path, const char *name,
                 void *value, size_t size);
ssize_t fgetxattr(int fd, const char *name,
                 void *value, size_t size);
 

DESCRIPTION

Extended attributes are name:value pairs associated with inodes (files, directories, symbolic links, etc.). They are extensions to the normal attributes which are associated with all inodes in the system (i.e., the stat(2) data). A complete overview of extended attributes concepts can be found in attr(5).

getxattr() retrieves the value of the extended attribute identified by name and associated with the given path in the filesystem. The length of the attribute value is returned.

lgetxattr() is identical to getxattr(), except in the case of a symbolic link, where the link itself is interrogated, not the file that it refers to.

fgetxattr() is identical to getxattr(), only the open file referred to by fd (as returned by open(2)) is interrogated in place of path.

An extended attribute name is a simple null-terminated string. The name includes a namespace prefix; there may be several, disjoint namespaces associated with an individual inode. The value of an extended attribute is a chunk of arbitrary textual or binary data of specified length.

An empty buffer of size zero can be passed into these calls to return the current size of the named extended attribute, which can be used to estimate the size of a buffer which is sufficiently large to hold the value associated with the extended attribute.

The interface is designed to allow guessing of initial buffer sizes, and to enlarge buffers when the return value indicates that the buffer provided was too small.  

RETURN VALUE

On success, a nonnegative number is returned indicating the size of the extended attribute value. On failure, -1 is returned and errno is set appropriately.  

ERRORS

ENOATTR
The named attribute does not exist, or the process has no access to this attribute. (ENOATTR is defined to be a synonym for ENODATA in <attr/xattr.h>.)
ENOTSUP
Extended attributes are not supported by the filesystem, or are disabled.
ERANGE
The size of the value buffer is too small to hold the result.

In addition, the errors documented in stat(2) can also occur.  

VERSIONS

These system calls have been available on Linux since kernel 2.4; glibc support is provided since version 2.3.  

CONFORMING TO

These system calls are Linux-specific.  

SEE ALSO

getfattr(1), setfattr(1), listxattr(2), open(2), removexattr(2), setxattr(2), stat(2), attr(5), symlink(7)  

COLOPHON

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Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
SEE ALSO
COLOPHON

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Time: 21:42:57 GMT, July 12, 2014