pro TREE,curdir,maxlevel=maxlevel,file=file $
	,level=level,flag=flag,tab=tab,stat=stat
;+
; NAME:		TREE
;	
; PURPOSE:	Draws a subdirectory tree on UNIX systems
;	
; CATEGORY:	Stuff that noone ever bothers to write
;	
; CALLING SEQUENCE:
;		TREE [,dname,maxlevel=n,file=fname]
;	
; INPUTS:	All inputs are optional
;	CURDIR		String variable containing the name of the directory
;			at the root of the tree. (Defaults to '~')
; KEYWORDS:
;	MAXLEVEL	Integer indicating the number of levels of
;			subdirectories to display.  (Default is to search to
;			a depth of 10 {this is done to avoid infinite loops})
;			Existance of subdirectories beyond MAXLEVEL are
;			indicated by '-->>'.
;
;	FILE		String variable specifying the output file name.
;			Special case use of /FILE causes output to go to a file
;			named 'tree.out'. (Default is to output to the screen)
;
; ****	Other Keywords are used to pass data recursively and are, therefore,
;	for internal use only and should NOT be utilized by the user.
;
; OUTPUTS:
;	May output to either the screen or a file.
;	
; COMMON BLOCKS:	None
;
; SIDE EFFECTS:		None
;	
; RESTRICTIONS:
;			Written to run on UNIX systems
;
;			WARNING! Some patches to operating systems (eg. SUN)
;			have been found to generate infinite loops.  Do not
;			make MAXLEVEL large unnecessarily.
;
;			Really deep searches (MAXLEVEL large) may trash the
;			display when line wrapping is enabled.
;	
; PROCEDURE:
;	STRAIGHTFORWARD (seems to be the default value of this field).
;
; MODIFICATION HISTORY:
;	Written 2/5/93 by J. M. Zawodny, NASA Langley Research Center.
;	zawodny@arbd0.larc.nasa.gov
;-

; Somethings are only done at the top level
	if (n_elements(level) eq 0) then begin

	; Set default values
		if(n_elements(curdir) le 0) then curdir = '~'
		if not keyword_set(maxlevel) then maxlevel = 10
		level = 0

	; Get the starting directory
		spawn,'cd '+curdir,list
		tab = '      '

	; Do we write this to a file
		if keyword_set(file) then begin
		; Get variable type of file
			s = size(file)
		; Is file a string?
			if(s(1) eq 7) then fname=file else fname='tree.out'
			openw,lun,fname,/get_lun
			flag = lun
			printf,flag,list
		endif else begin
			flag = 0
			print,list
		endelse
	endif

; Find out what is in the directory
	spawn,'ls -1 -F '+curdir+' | grep "/"',list
	if(list(0) eq '') then begin
		stat = 0
		return
	endif

; Are we beyond desired depth
	if(level ge maxlevel) then begin
		if keyword_set(flag) then printf,flag,tab+'|-->>' $
			 else print,tab+'|-->>'
		stat = -1
		return
	endif

; For all subdirectories in this directory
	len = n_elements(list)-1
	for k=0,len do begin
		name = list(k)
		name = strmid(name,0,strpos(name,'/'))
	; Output a line
		if (k ne len) then tb = tab+'|     ' else tb = tab+'      '
		v = tab+'|-----'+name
		if keyword_set(flag) then printf,flag,v else print,v

	; Recurse through all subdirectory levels
		tree,curdir+'/'+name,level=(level+1),maxlevel=maxlevel, $
			flag=flag,tab=tb,stat=stat

		if(k ne len) and stat then begin
			tb = tab+'|'
			if keyword_set(flag) then printf,flag,tb $
				else print,tb
		endif

	endfor
	stat = 1

	if keyword_set(file) then begin
		close,lun
		free_lun,lun
	endif
return
end