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VOP_SETATTR.9freebsd

BSD mandoc

NAME

VOP_GETATTR VOP_SETATTR - get and set attributes on a file or directory

SYNOPSIS

In sys/param.h In sys/vnode.h Ft int Fn VOP_GETATTR struct vnode *vp struct vattr *vap struct ucred *cred struct thread *td Ft int Fn VOP_SETATTR struct vnode *vp struct vattr *vap struct ucred *cred struct thread *td

DESCRIPTION

These entry points manipulate various attributes of a file or directory, including file permissions, owner, group, size, access time and modification time.

The arguments are:

Fa vp

The vnode of the file.

Fa vap

The attributes of the file.

Fa cred

The user credentials of the calling process.

Fa td

The thread.

Attributes which are not being modified by Fn VOP_SETATTR should be set to the value VNOVAL Fn VATTR_NULL may be used to clear all the values, and should generally be used to reset the contents of Fa *vap prior to setting specific values.

LOCKS

Fn VOP_GETATTR expects the vnode to be locked on entry and will leave the vnode locked on return. The lock type can be either shared or exclusive.

Fn VOP_SETATTR expects the vnode to be locked on entry and will leave the vnode locked on return. The lock type must be exclusive.

RETURN VALUES

Fn VOP_GETATTR returns 0 if it was able to retrieve the attribute data via Fa *vap , otherwise an appropriate error is returned. Fn VOP_SETATTR returns zero if the attributes were changed successfully, otherwise an appropriate error is returned.

PSEUDOCODE

 int
 vop_getattr(struct vnode *vp, struct vattr *vap,
             struct ucred *cred, struct thread *td)
 {
     /*
      * Fill in the contents of *vap with information from
      * the file system.
      */
     ...;
 
     return 0;
 }
 
 int
 vop_setattr(struct vnode *vp, struct vattr *vap,
             struct ucred *cred, struct thread *td)
 {
     /*
      * Check for unsettable attributes.
      */
     if ((vap->va_type != VNON) || (vap->va_nlink != VNOVAL) ||
         (vap->va_fsid != VNOVAL) || (vap->va_fileid != VNOVAL) ||
         (vap->va_blocksize != VNOVAL) || (vap->va_rdev != VNOVAL) ||
         ((int)vap->va_bytes != VNOVAL) || (vap->va_gen != VNOVAL)) {
         return (EINVAL);
     }
 
     if (vap->va_flags != VNOVAL) {
         /*
          * Set the immutable and append flags of the file.
          */
     }
 
     if (vap->va_uid != (uid_t)VNOVAL || vap->va_gid != (gid_t)VNOVAL) {
         /*
          * Change owner and/or group of the file.
          */
     }
 
     if (vap->va_size != VNOVAL) {
         /*
          * Truncate the file to the specified size.
          */
     }
 
     if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
         /*
          * Change access and/or modification time of file.
          */
     }
 
     if (vap->va_mode != (mode_t)VNOVAL) {
         /*
          * Change permissions of file.
          */
     }
 
     return 0;
 }
 

ERRORS

Bq Er EPERM

The file is immutable.

Bq Er EACCES

The caller does not have permission to modify the file or directory attributes.

Bq Er EROFS

The file system is read-only.

SEE ALSO

VFS(9), vnode(9), VOP_ACCESS9

AUTHORS

This manual page was written by An Doug Rabson .