265 lines
6.3 KiB
Groff
265 lines
6.3 KiB
Groff
'\"macro stdmacro
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.if n .pH g2.attr_set @(#)attr_set 1.1 of 6/12/95
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.TH ATTR_SET 2
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.SH NAME
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attr_set, attr_setf \- set the value of a user attribute of a filesystem object
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.Op c p a
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.SH C SYNOPSIS
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.PP
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.sp
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.nf
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.B #include <sys/attributes.h>
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.sp
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.B "int attr_set (const char \(**path, const char \(**attrname, "
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.B " const char \(**attrvalue, const int valuelength,"
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.B " int flags);"
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.PP
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.B "int attr_setf (int fd, const char \(**attrname, "
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.B " const char \(**attrvalue, const int valuelength,"
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.B " int flags);"
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.Op
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.SH OVERVIEW
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The
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.I attr
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group of system calls implement the ability for a user to attach
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name/value pairs to objects within the filesystem.
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.P
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They could be used to store meta-information about the file.
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For example "character-set=kanji" could tell a document browser to
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use the Kanji character set when displaying that document
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and "thumbnail=..." could provide a reduced resolution overview of a
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high resolution graphic image.
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.P
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The
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.I names
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can be up to MAXNAMELEN bytes in length, terminated by the first 0 byte.
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The intent is that they be printable ASCII (or other character set)
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names for the attribute.
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.P
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The
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.I values
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can be up to ATTR_MAX_VALUELEN (currently 64KB) of arbitrary binary data.
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.P
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Attributes can be attached to all types of inodes:
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regular files, directories, symbolic links, device nodes, etc.
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.P
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There are 2 disjoint attribute name spaces associated with every
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filesystem object.
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They are the
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.B root
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and
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.B user
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address spaces.
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The
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.B root
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address space is accessable only to the super-user,
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and then only by specifying a flag argument to the function call.
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Other users will not see or be able to modify attributes in the
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.B root
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address space.
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The
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.B user
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address space is protected by the normal file permissions mechanism,
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so the owner of the file can decide who is able to see and/or modify
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the value of attributes on any particular file.
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.P
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Attributes are currently supported only in the XFS filesystem type.
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.SH DESCRIPTION
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The
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.I attr_set
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and
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.I attr_setf
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functions provide a way to create attributes and set/change their values.
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.P
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.I Path\^
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points to a path name for a filesystem object, and
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.I fd\^
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refers to the file descriptor associated with a file.
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If the attribute
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.I attrname
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does not exist, an attribute with the given name and value will be created
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and associated with that indicated filesystem object.
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If an attribute with that name already exists on that filesystem object,
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the existing value is replaced with the new value given in this call.
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The new attribute value is copied from the
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.I attrvalue
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buffer for a total of
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.I valuelength
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bytes.
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The
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.I flags
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argument can contain the following symbols bitwise OR\'ed together:
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.TP
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.SM
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\%ATTR_ROOT
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Look for
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.I attrname
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in the
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.B root
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address space, not in the
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.B user
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address space.
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(limited to use by super-user only)
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.TP
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.SM
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\%ATTR_DONTFOLLOW
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Do not follow symbolic links when resolving a
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.I path
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on an
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.I attr_set
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function call.
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The default is to follow symbolic links.
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.TP
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.SM
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\%ATTR_CREATE
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Return an error (EEXIST) if an attribute of the given name
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already exists on the indicated filesystem object,
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otherwise create an attribute with the given name and value.
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This flag is used to implement a pure create operation,
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without this flag
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.I attr_set
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will create the attribute if it does not already exist.
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An error (EINVAL) will be returned if both ATTR_CREATE and ATTR_REPLACE
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are set in the same call.
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.TP
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.SM
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\%ATTR_REPLACE
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Return an error (ENOATTR) if an attribute of the given name
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does not already exist on the indicated filesystem object,
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otherwise replace the existing attribute\'s value with the given value.
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This flag is used to implement a pure replacement operation,
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without this flag
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.I attr_set
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will create the attribute if it does not already exist.
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An error (EINVAL) will be returned if both ATTR_CREATE and ATTR_REPLACE
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are set in the same call.
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.PP
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.I attr_set
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will fail if one or more of the following are true:
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.TP 17
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.SM
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\%[ENOATTR]
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The attribute name given is not associated with the indicated
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filesystem object and the ATTR_REPLACE flag bit was set.
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.TP
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.SM
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\%[E2BIG]
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The value of the given attribute is too large, it exceeds the
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maximum allowable size of an attribute value.
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.TP
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.SM
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\%[EEXIST]
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The attribute name given is already associated with the indicated
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filesystem object and the ATTR_CREATE flag bit was set.
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.TP
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.SM
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\%[ENOENT]
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The named file does not exist.
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.TP
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.SM
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\%[EPERM]
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The effective user
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.SM ID
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does not match the owner of the file
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and the effective user
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.SM ID
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is not super-user.
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.TP
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.SM
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\%[ENOTDIR]
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A component of the
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path prefix
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is not a directory.
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.TP
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.SM
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\%[EACCES]
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Search permission is denied on a
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component of the
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path prefix.
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.TP
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.SM
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\%[EINVAL]
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A bit was set in the
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.I flag
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argument that is not defined for this system call,
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or both the ATTR_CREATE and ATTR_REPLACE flags bits were set.
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.TP
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.SM
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\%[EFAULT]
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.I Path,
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.I attrname,
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or
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.I attrvalue
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points outside the allocated address space of the process.
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.TP
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.SM
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\%[ELOOP]
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A path name lookup involved too many symbolic links.
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.TP
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.SM
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\%[ENAMETOOLONG]
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The length of
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.I path
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exceeds
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.SM
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.RI { MAXPATHLEN },
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or a pathname component is longer than
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.SM
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.RI { MAXNAMELEN }.
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.PP
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.I attr_setf\^
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will fail if:
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.TP 15
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.SM
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\%[ENOATTR]
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The attribute name given is not associated with the indicated
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filesystem object and the ATTR_REPLACE flag bit was set.
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.TP
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.SM
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\%[E2BIG]
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The value of the given attribute is too large, it exceeds the
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maximum allowable size of an attribute value.
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.TP
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.SM
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\%[EEXIST]
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The attribute name given is already associated with the indicated
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filesystem object and the ATTR_CREATE flag bit was set.
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.TP
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.SM
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\%[EINVAL]
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A bit was set in the
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.I flag
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argument that is not defined for this system call,
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or both the ATTR_CREATE and ATTR_REPLACE flags bits were set, or
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.I fd\^
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refers to a socket, not a file.
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.TP
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.SM
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\%[EFAULT]
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.I Attrname,
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or
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.I attrvalue
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points outside the allocated address space of the process.
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.TP
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.SM
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\%[EBADF]
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.I Fd\^
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does not refer to a valid descriptor.
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.SH "SEE ALSO"
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attr(1),
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.br
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attr_get(2), attr_getf(2),
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.br
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attr_list(2), attr_listf(2)
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.br
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attr_multi(2), attr_multif(2)
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.br
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attr_remove(2), attr_removef(2),
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.SH "DIAGNOSTICS"
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Upon successful completion, a value of 0 is returned.
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Otherwise, a value of \-1 is returned and
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.I errno\^
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is set to indicate the error.
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.\" @(#)attr_set.2 1.0 of 6.12.95
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.Ee
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