in reply to Re: Avoid headaches from Strawberry Perl 5.10.0 and binary SVK
in thread Avoid headaches from Strawberry Perl 5.10.0 and binary SVK

Similar things can happen in Unix as well if you're not careful with how you set up %ENV and where you modify it.

I don't think so. If you run a script on Unix and it mucks with ENV, then when it terminates, that doesn't affect your ENV. There is no global ENV in Unix, unlike Windows.

My criteria for good software:
  1. Does it work?
  2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
  • Comment on Re^2: Avoid headaches from Strawberry Perl 5.10.0 and binary SVK

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Re^3: Avoid headaches from Strawberry Perl 5.10.0 and binary SVK
by BrowserUk (Patriarch) on Jan 09, 2008 at 16:46 UTC

    This has nothing to do with the global environment variables. They are not being modified in any way here.

    Because .BAT files are interpreted by the shell (cmd.exe) itself, set commands modify it's own copy of the environment vars and as it persists after the .BAt file ends, so do the changes made to it. Within that command shell instance only.

    No other existing instances are affected. And no new instances will be affected, unless they are started as children of this instance, in which case they will inherit the modifications made to their parent. When this instance (and any children it started) ends, the modifications disappear.

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
      Changes made by a command in Unix cannot affect the shell the command was invoked from. This is because all commands are run in child processes. Apparently, Windows runs things in child threads?
      My criteria for good software:
      1. Does it work?
      2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?
[reply]
        Apparently, Windows runs things in child threads?

        No. No threads involved either. When unix runs a shell script, it forks the existing shell and runs the script in the child process. And environment changes are made to the child's environment block and so disappear when that shell exits. Whilst it runs, the original shell sits in the background and waits. And it is to that parent shell instance that you are returned, when the script ends.

        In Windows, the .bat file is run within the same instance into which the command is entered and it is to that same instance that you are returned when the bat file ends. So any changes the .bat file makes to that shell instances environment are persisted.

        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority".
        In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]

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