FUNCTION IsSymLink, file

;+
; NAME:
;	IsSymLink
; PURPOSE:
;	Checks whether a file or directory is a symbolic link
; CATEGORY:
;	Environment
; CALLING SEQUENCE:
;	B = IsSymLink(file)
; INPUTS:
;	file		scalar; type: string
;					name of file or directory to be tested
; OUTPUTS:
;	B			scalar; type: integer
;					0: not a symbolic link
;					1: it's symbolic link
;				On non-Unix systems, always 0 is returned
; INCLUDE:
	@compile_opt.pro		; On error, return to caller
; RESTRICTIONS:
; >	Has only been tested on Linux (bash shell) under IDL 5.3 and 5.5
; >	The islink script is needed for IDL version <= 5.4 and must be in the Linux path
; >	Does not work on a path that contains a symbolic link, e.g.
;	if /usr/local/rsi is a symbolic link then /usr/local/rsi/lib will
;	return zero.
; PROCEDURE:
; >	Only useful on Unix/Linux systems.
;	If !version.os_family is not 'unix' then always 0 is returned.
;
; >	If !version.os_family is 'unix' then:
;	- for IDL 5.3 and earlier the script islink is spawned. The
;		output from this script (0 or 1) is captured in the 'result'
;		argument of spawn.
;	- for IDL 5.4 and later, a 'test -L' is spawned, and the
;		exit_status keyword is used directly (this makes the test
;		independent of the islink script).
; MODIFICATION HISTORY:
;	JULY-2001, Paul Hick (UCSD/CASS; pphick@ucsd.edu)
;-

CASE !version.os_family OF
'unix': BEGIN
	IF !version.release LT 5.4 THEN BEGIN
		spawn, 'which islink', prog				; Search for script
		b = prog[0] EQ ''
		CASE b OF
		0: spawn, prog[0]+' '+file[0], b
		1: message, /info, 'script "islink" not found in path'
		ENDCASE
	ENDIF ELSE	$
		spawn, 'test -L "'+file[0]+'"', exit_status=b

	b = fix(b[0])
	IF NOT b THEN message, /info, 'symbolic link, '+file[0]
END
ELSE  : b = 1
ENDCASE

RETURN, 1-b  &  END