examples/functions/autoload

   1 #
   2 # An almost ksh-compatible `autoload'.  A function declared as `autoload' will
   3 # be read in from a file the same name as the function found by searching the
   4 # $FPATH (which works the same as $PATH), then that definition will be run.
   5 #
   6 # To do this without source support, we define a dummy function that, when
   7 # executed, will load the file (thereby re-defining the function), then
   8 # execute that newly-redefined function with the original arguments.
   9 #
  10 # It's not identical to ksh because ksh apparently does lazy evaluation
  11 # and looks for the file to load from only when the function is referenced.
  12 # This one requires that the file exist when the function is declared as
  13 # `autoload'.
  14 #
  15 # usage: autoload func [func...]
  16 #
  17 # The first cut of this was by Bill Trost, trost@reed.bitnet
  18 #
  19 # Chet Ramey
  20 # chet@ins.CWRU.Edu
  21
  22 #
  23 # Declare a function ($1) to be autoloaded from a file ($2) when it is first
  24 # called.  This defines a `temporary' function that will `.' the file
  25 # containg the real function definition, then execute that new definition with
  26 # the arguments given to this `fake' function.  The autoload function defined
  27 # by the file and the file itself *must* be named identically.
  28 #
  29
  30 aload()
  31 {
  32         eval $1 '() {  . '$2' ; '$1' "$@" ; return $? ; }'
  33 }
  34
  35 #
  36 # Search $FPATH for a file the same name as the function given as $1, and
  37 # autoload the function from that file.  There is no default $FPATH.
  38 #
  39
  40 autoload()
  41 {
  42         #
  43         # Save the list of functions; we're going to blow away the arguments
  44         # in a second.  If any of the names contain white space, TFB.
  45         #
  46
  47         local args="$*"
  48
  49         #
  50         # This should, I think, list the functions marked as autoload and not
  51         # yet defined, but we don't have enough information to do that here.
  52         #
  53         if [ $# -eq 0 ] ; then
  54                 echo "usage: autoload function [function...]"
  55                 return 1
  56         fi
  57
  58         #
  59         # If there is no $FPATH, there is no work to be done
  60         #
  61
  62         if [ -z "$FPATH" ] ; then
  63                 echo autoload: FPATH not set
  64                 return 1
  65         fi
  66
  67         #
  68         # This treats FPATH exactly like PATH: a null field anywhere in the
  69         # FPATH is treated the same as the current directory.
  70         #
  71         # The path splitting command is taken from Kernighan and Pike
  72         #
  73
  74         fp=$(echo $FPATH | sed 's/^:/.:/
  75                                 s/::/:.:/g
  76                                 s/:$/:./
  77                                 s/:/ /g')
  78
  79         for FUNC in $args ; do
  80                 #
  81                 # We're blowing away the arguments to autoload here...
  82                 # We have to; there are no arrays.
  83                 #
  84                 set $fp
  85
  86                 while [ $# -ne 0 ] ; do
  87                         if [ -f $1/$FUNC ] ; then
  88                                 break                   # found it!
  89                         fi
  90                         shift
  91                 done
  92
  93                 if [ $# -eq 0 ] ; then
  94                         echo "$FUNC: autoload function not found"
  95                         continue
  96                 fi
  97
  98 #               echo auto-loading $FUNC from $1/$FUNC
  99                 aload $FUNC $1/$FUNC
 100         done
 101
 102         return 0
 103 }