|| FreeBSD Miscellaneous Information Manual
sticky text and append-only directories
A special file mode, called the
(mode S_ISTXT), is used to indicate special treatment for directories. It is ignored for regular files. See
or the file
for an explanation of file modes.
A directory whose `sticky bit' is set becomes an append-only directory, or, more accurately, a directory in which the deletion of files is restricted. A file in a sticky directory may only be removed or renamed by a user if the user has write permission for the directory and the user is the owner of the file, the owner of the directory, or the super-user. This feature is usefully applied to directories such as
which must be publicly writable but should deny users the license to arbitrarily delete or rename each others' files.
Any user may create a sticky directory. See chmod(1) for details about modifying file modes.
sticky command appeared in Version 32V AT&T UNIX.
will create a file with the sticky bit set.