[PowerShell] command line output and adding system environment variables

View a system variable

Q： How to use Windows PowerShell View my environment variables Path, Which folders are there and the order in which they are displayed ？

A： Use $ env And get the Path The value of the variable . By default , It is displayed as a continuous string , It may be a little hard to read . The order is as follows ：

$env：path

however , If you use –split Operator breaks a string at a semicolon , It is more readable ：

$env：path -split“;”

other
such as ： Check the system

$env:os

such as ： System cores CPU

$env:NUMBER_OF_PROCESSORS

Be careful ： View these environment variables , It must exist in the environment variable , Or you added it yourself .

Modify environment variables

First understand a thing ： stay Windows On , You can define environment variables in three scopes ：

1. System level （Machine）
2. User level （User）
3. Session level （Process）, Which means turn it off powershell Is the failure , This list of variables is inherited from the parent process , And it's based on Machine and User Variables in the scope are constructed .

user & System & Session level

In the picture ：· User variables Corresponding user level scope , System variables Corresponding to the system level scope .

Add... On the basis of the original environment variables , And specify the scope （ user or System or conversation ）, One command is done ：

$addPath=‘c:\add\you\path\here’; $target=‘User’ ; $path = [Environment]::GetEnvironmentVariable(‘Path’, $target); $newPath = $path + ‘;’ + $addPath; [Environment]::SetEnvironmentVariable(“Path”, $newPath, $target)

Be careful ：

1. $addPath The equal sign is followed by the path you want to add
2. $target The equal sign is followed by the scope ,Machine（ System level ） / User（ User level ） / Process（ Session level ） Choose one of three , The first two amendments will take effect in time , And turn off powershell The conversation is still valid .
3. Other places don't need to be changed , Direct execution

Session level modification - Method 2

Add a new environment variable

$env:amostest=“amos for test desc”

Add... To the existing environment variables

$env:path+=";c:\your_path"

Reference resources

About Environment Variables
EnvironmentVariableTarget Enum