util_link_responding_p

util_link_responding_p   url   { list_of_bad_codes "404" }

Returns 1 if the URL is responding (generally we think that anything other than 404 (not found) is okay).

Source code:

    if [catch { set status [util_get_http_status $url] } errmsg] {
	# got an error; definitely not valid
	return 0
    } else {
	# we got the page but it might have been a 404 or something
	if { [lsearch $list_of_bad_codes $status] != -1 } {
	    return 0
	} else {
	    return 1
	}
    }