bsd/man/man7/sticky.7

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  31 .Dd June 5, 1993
  32 .Dt STICKY 7
  33 .Os
  34 .Sh NAME
  35 .Nm sticky
  36 .Nd sticky text and append-only directories
  37 .Sh DESCRIPTION
  38 A special file mode, called the
  39 .Em sticky bit
  40 (mode S_ISVTX),
  41 is used to indicate special treatment
  42 for directories.
  43 It is ignored for regular files.
  44 See
  45 .Xr chmod 2
  46 or
  47 the file
  48 .In sys/stat.h
  49 for an explanation of file modes.
  50 .Sh STICKY DIRECTORIES
  51 A directory whose `sticky bit' is set
  52 becomes an append-only directory, or, more accurately,
  53 a directory in which the deletion of files is restricted.
  54 A file in a sticky directory may only be removed or renamed
  55 by a user if the user has write permission for the directory and
  56 the user is the owner of the file, the owner of the directory,
  57 or the super-user.
  58 This feature is usefully applied to directories such as
  59 .Pa /tmp
  60 which must be publicly writable but
  61 should deny users the license to arbitrarily
  62 delete or rename each others' files.
  63 .Pp
  64 Any user may create a sticky directory.
  65 See
  66 .Xr chmod 1
  67 for details about modifying file modes.
  68 .Sh HISTORY
  69 A
  70 .Nm
  71 command appeared in
  72 .At 32v .
  73 .Sh BUGS
  74 Neither
  75 .Xr open 2
  76 nor
  77 .Xr mkdir 2
  78 will create a file with the sticky bit set.