$LASTEXITCODE undefined after command

Question

I'm going crazy, can someone explain me why the value of $lastexitcode is undefined?

look to my simple attempt: if I launch command dir, I get the correct output so $LASTEXITCODE must be 0.

unfortunately, if I try:

$LASTEXITCODE

I haven't any return value. it's the same situation if I give before an command like "diiiiir" or something similar that doesn't exist.

Answer 1

$LASTEXITCODE is only set by executables or batch files when they return. PowerShell commands can be checked with $?. See here for more information.

Answer 2

In particular $LASTEXITCODE is set by "Legacy" exectutables... it is equivalent to the old DOS/Windows %ERRORLEVEL% variable. Here is the best way to manage $LASTEXITCODE within PowerShell:

cmd /c "exit 0" #Reset $LASTEXITCODE between runs while debugging

A batch (.bat)/command (.cmd) file will set it when called from PowerShell:

exit /b <exitcode>

For example, create a command file called SetLASTEXITCODE.cmd with the following line:

exit /b 2

Then, call the command file from PowerShell:

cmd /c "SetLASTEXITCODE.cmd"

Output should be:

exit /b 2

Now test $LASTEXITCODE:

$LASTEXITCODE

Output is:

2

Note: on so called "Legacy" executables (also includes the old .com files), if the developer/programmer did not set the ERRORLEVEL from whatever programming language the exe was written in (usually via an API call), then ERRORLEVEL/LASTEXITCODE will not be set! I used to write these way back when in the early '80s and there was a distinction back then between internal commands like your 'dir' example which does not set ERRORLEVEL and external commands in (.com) or exe files - a long since forgotten detail.

One last example... modify the command file to include the following and repeat above test... it sets both ERRORLEVEL within command file and exits with %ERRORLEVEL% setting $LASTEXITCODE...

cmd /c "exit /b 2"
echo %ERRORLEVEL%
exit /b %ERRORLEVEL%

Have fun...