Annotation of /sml/trunk/src/smlnj-lib/Unix/unix-env.sml

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1 :	monnier	2	(* unix-env.sml
2 :			*
3 :			* COPYRIGHT (c) 1993 by AT&T Bell Laboratories. See COPYRIGHT file for details.
4 :			*
5 :			* A UNIX environment is a list of strings of the form "name=value", where
6 :			* the "=" character does not appear in name.
7 :			* NOTE: binding the user's environment as an ML value and then exporting the
8 :			* ML image can result in incorrect behavior, since the environment bound in the
9 :			* heap image may differ from the user's environment when the exported image
10 :			* is used.
11 :			*)
12 :
13 :			structure UnixEnv : UNIX_ENV =
14 :			struct
15 :
16 :			local
17 :			fun isEqual #"=" = true | isEqual _ = false
18 :			in
19 :			fun splitBinding s = (case (String.fields isEqual s)
20 :			of [a, b] => (a, b)
21 :			| _ => (s, "")
22 :			(* end case *))
23 :			end
24 :
25 :			(* return the value, if any, bound to the name. *)
26 :			fun getFromEnv (name, env) = let
27 :			fun look [] = NONE
28 :			| look (s::r) = let
29 :			val (n, v) = splitBinding s
30 :			in
31 :			if (n = name) then (SOME v) else look r
32 :			end
33 :			in
34 :			look env
35 :			end
36 :
37 :			(* return the value bound to the name, or a default value *)
38 :			fun getValue {name, default, env} = (case getFromEnv(name, env)
39 :			of (SOME s) => s
40 :			| NONE => default
41 :			(* end case *))
42 :
43 :			(* remove a binding from an environment *)
44 :			fun removeFromEnv (name, env) = let
45 :			fun look [] = []
46 :			| look (s::r) = let
47 :			val (n, v) = splitBinding s
48 :			in
49 :			if (n = name) then r else (s :: look r)
50 :			end
51 :			in
52 :			look env
53 :			end
54 :
55 :			(* add a binding to an environment, replacing an existing binding
56 :			* if necessary.
57 :			*)
58 :			fun addToEnv (nameValue, env) = let
59 :			val (name, _) = splitBinding nameValue
60 :			fun look [] = [nameValue]
61 :			| look (s::r) = let
62 :			val (n, v) = splitBinding s
63 :			in
64 :			if (n = name) then r else (s :: look r)
65 :			end
66 :			in
67 :			look env
68 :			end
69 :
70 :			(* return the user's environment *)
71 :			val environ = Posix.ProcEnv.environ
72 :
73 :			(* return the binding of an environment variable in the
74 :			* user's environment.
75 :			*)
76 :			fun getEnv name = getFromEnv(name, environ())
77 :
78 :			end; (* UnixEnv *)
79 :

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