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 :	jhr	967	structure SS = Substring
17 :
18 :	monnier	2	local
19 :	jhr	967	fun notEqual #"=" = false | notEqual _ = true
20 :			val split = SS.splitl notEqual
21 :	monnier	2	in
22 :	jhr	967	fun splitBinding s = let
23 :			val (a, b) = split(SS.all s)
24 :			in
25 :			if SS.isEmpty b
26 :			then (s, "")
27 :			else (SS.string a, SS.string(SS.triml 1 b))
28 :			end
29 :	monnier	2	end
30 :
31 :			(* return the value, if any, bound to the name. *)
32 :			fun getFromEnv (name, env) = let
33 :			fun look [] = NONE
34 :			| look (s::r) = let
35 :			val (n, v) = splitBinding s
36 :			in
37 :			if (n = name) then (SOME v) else look r
38 :			end
39 :			in
40 :			look env
41 :			end
42 :
43 :			(* return the value bound to the name, or a default value *)
44 :			fun getValue {name, default, env} = (case getFromEnv(name, env)
45 :			of (SOME s) => s
46 :			| NONE => default
47 :			(* end case *))
48 :
49 :			(* remove a binding from an environment *)
50 :			fun removeFromEnv (name, env) = let
51 :			fun look [] = []
52 :			| look (s::r) = let
53 :			val (n, v) = splitBinding s
54 :			in
55 :			if (n = name) then r else (s :: look r)
56 :			end
57 :			in
58 :			look env
59 :			end
60 :
61 :			(* add a binding to an environment, replacing an existing binding
62 :			* if necessary.
63 :			*)
64 :			fun addToEnv (nameValue, env) = let
65 :			val (name, _) = splitBinding nameValue
66 :			fun look [] = [nameValue]
67 :			| look (s::r) = let
68 :			val (n, v) = splitBinding s
69 :			in
70 :			if (n = name) then r else (s :: look r)
71 :			end
72 :			in
73 :			look env
74 :			end
75 :
76 :			(* return the user's environment *)
77 :			val environ = Posix.ProcEnv.environ
78 :
79 :			(* return the binding of an environment variable in the
80 :			* user's environment.
81 :			*)
82 :			fun getEnv name = getFromEnv(name, environ())
83 :
84 :			end; (* UnixEnv *)
85 :

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