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From "Benjamin Bentmann (JIRA)" <j...@apache.org>
Subject [jira] Commented: (EXEC-30) Make environment variables respect casing rules of platforms
Date Tue, 18 Nov 2008 16:49:44 GMT

    [ https://issues.apache.org/jira/browse/EXEC-30?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12648648#action_12648648
] 

Benjamin Bentmann commented on EXEC-30:
---------------------------------------

bq. IMHO it is good practice to stick on a casing that works on all target platform instead
of implementing workarounds for badly written program.
Just to make sure it's clearly stated: For the code as is, the line
{code}
System.out.println("PATH = " + EnvironmentUtil.getProcEnvironment().get("PATH"));
{code}
usually prints "PATH = null" on Windows (tried with NT, 2K, XP, Vista).

> Make environment variables respect casing rules of platforms
> ------------------------------------------------------------
>
>                 Key: EXEC-30
>                 URL: https://issues.apache.org/jira/browse/EXEC-30
>             Project: Commons Exec
>          Issue Type: Improvement
>    Affects Versions: 1.0
>         Environment: Windows
>            Reporter: Benjamin Bentmann
>            Assignee: Siegfried Goeschl
>            Priority: Critical
>             Fix For: 1.0
>
>         Attachments: EXEC-30.patch
>
>
> Intro: Environment variables on Windows are case-insensitive (see [ExpandEnvironmentStrings|http://msdn.microsoft.com/en-us/library/ms724265(VS.85).aspx]).
As a little experiment, run the following code snippet on Windows with Java 1.5
> {code:java}
> System.out.println(System.getenv("PATH"));
> System.out.println(System.getenv("path"));
> System.out.println(System.getenv("Path"));
> System.out.println(System.getenv().get("PATH"));
> System.out.println(System.getenv().get("path"));
> System.out.println(System.getenv().get("Path"));
> {code}
> which can for example output
> {noformat}
> <successfully resolved variable>
> <successfully resolved variable>
> <successfully resolved variable>
> null
> null
> <successfully resolved variable>{noformat}
> IMHO, this is an example of how an API should *not* be designed. The two overloads of
{{System.getenv()}} look very similar but behave completely different. Even having this documented,
this subtle peculiarity makes Java programming prone to errors that prevent platform-independence.
> Commons Exec is currently providing a case-sensitive view of the Windows shell environment.
This makes it effectively impossible for client to code to reliably lookup an environment
variable without performing further tweaks to the map returned from {{EnvironmentUtil}}. Furthermore,
these tweaks would have to be performed only depending on the current OS, so the client code
would need to consider platform details. I believe this violates the basic principle of platform-independence
intended by Java.
> So here my suggestion: Have Commons Exec provide a case-preserving map that obeys the
casing rules of the platform for key lookup. This way, the simple code line
> {code:java}
> EnvironmentUtils.getProcEnvironment().get("PATH")
> {code}
> will consistently return the specified variable on Windows and Unix.
> Just to mention it: An alternative approach might be to have the map always be case-sensitive
but normalize variable names to upper-case on case-insensitive platforms.
> Regardless how this issue ends, the documentation for {{getProcEnvironment()}} should
clearly state how it deals with casing.

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