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.\"     @(#)revoke.2	8.1 (Berkeley) 6/4/93
.\"
.Dd January 25, 2016
.Dt REVOKE 2
.Os
.Sh NAME
.Nm revoke
.Nd revoke file access
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn revoke "const char *path"
.Sh DESCRIPTION
The
.Fn revoke
system call invalidates all current open file descriptors in the system
for the file named by
.Fa path .
Subsequent operations on any such descriptors
fail, with the exceptions that a
.Fn read
from a character device file which has been revoked
returns a count of zero (end of file),
and a
.Fn close
system call will succeed.
If the file is a special file for a device which is open,
the device close function
is called as if all open references to the file had been closed
using a special close method which does not block.
.Pp
Access to a file may be revoked only by its owner or the super user.
The
.Fn revoke
system call is currently supported only for block and character special
device files.
It is normally used to prepare a terminal device for a new login session,
preventing any access by a previous user of the terminal.
.Sh RETURN VALUES
.Rv -std revoke
.Sh ERRORS
Access to the named file is revoked unless one of the following:
.Bl -tag -width Er
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1024 characters.
.It Bq Er ENOENT
The named file or a component of the path name does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EFAULT
The
.Fa path
argument
points outside the process's allocated address space.
.It Bq Er EINVAL
The implementation does not support the
.Fn revoke
operation on the named file.
.It Bq Er EPERM
The caller is neither the owner of the file nor the super user.
.El
.Sh SEE ALSO
.Xr revoke 1 ,
.Xr close 2
.Sh HISTORY
The
.Fn revoke
system call first appeared in
.Bx 4.3 Reno .
.Sh BUGS
The non-blocking close method is only correctly implemented for
terminal devices.