Command Section
STICKY(7)          FreeBSD Miscellaneous Information Manual          STICKY(7)

     sticky - sticky text and append-only directories

     A special file mode, called the sticky bit (mode S_ISTXT), is used to
     indicate special treatment for directories.  It is ignored for regular
     files.  See chmod(2) or the file <sys/stat.h> for an explanation of file

     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 /tmp 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.

     A sticky command appeared in Version 32V AT&T UNIX.

     Neither open(2) nor mkdir(2) will create a file with the sticky bit set.

FreeBSD 11.1-RELEASE-p4          June 5, 1993          FreeBSD 11.1-RELEASE-p4
Command Section