请帮助我使用重新排列路径的Power Shell脚本

Question

I have both Sybase and MSFT SQL Servers installed. There is a time when Sybase interferes with MS SQL because they have they have some overlapping commands.

So, I need two scripts:

A) When runs, script A backs up the current path, grabs all paths that contain sybase or SYBASE or SyBASE (you get the point) in them and move them all at the very end of the path, while preserving the order.

B) When it runs, script B restores the path from back-up.

Both script a and script b should affect the path immediately. So, if a.bat that calls patha.ps1, pathb.ps1 looks like so:

@REM Old path here
call patha.ps1
@REM At this point the effective path should be different.
call pathb.ps1
@REM Effective old path again

Please let me know if this does not make sense. I am not sure if call command is the best one to use.

I have never used PS before. I can try to formulate the same thing in Python (I know SO users tend to ask for "What have you tried so far"). Well, at this point I am VERY slow at writing anything in Power Shell language.

Please help.

Answer 1

First of all: call will be of no use here as you are apparently writing a batch file and PowerShell scripts have no association to run them by default. call is for batch files or subroutines.

Secondly, any PowerShell script you call from a batch file cannot change environment variables of the caller's environment. That's a fundamental property of how processes behave and since you are calling another process, this is never going to work.

I'm not so sure why you are even using a batch file here in the first place if you have PowerShell. You might just as well solve this in PowerShell completely.

However, what I get from your problem is that the best way to resolve this is probably the following: Create two batch files that each set the PATH appropriately. You can probably leave out both the MSSQL and Sybase paths from your usual PATH and add them solely in the batch files. Then create shortcuts to

cmd /k set_mssql_path.cmd

and

cmd /k set_sybase_path.cmd

each of which now is a shortcut to a shell to work with the appropriate database's tools. This is how the Visual Studio Command Prompt works and it's probably the cleanest solution you have. You can use the color and prompt commands in those batches to make the two different shells distinct so you always know what environment you have. For example the following two lines will color the console white on blue and set a prompt indicating MSSQL:

color 1f
prompt MSSQL$S$P$G

This can be quite handy, actually.

Generally, trying to rearrange the PATH environment variable isn't exactly easy. While you could trivially split at a ; this will fail for paths that itself contain a semicolon (and which need to be quoted then). Even in PowerShell this will take a while to get right so I think creating shortcuts specific to the tools is probably the nicest way to deal with this.