CODEWITHSUNDEEP
batch-file
OK999
OK999

Reputation: 1399

Is Windows %ERRORLEVEL% == $? in Linux

Trying my hands on windows batch files, in the below code that I found by searching in www.

@ECHO OFF
REM Call this with two arguments, and it will add them.
SET a=%1+%2
IF %ERRORLEVEL%==0 (goto errors-0) ELSE (goto errors-1)
REM Instead of using goto with the variable, this uses an IF-ELSE structure
:errors-0
REM This is if it was successful
ECHO %a%
goto exit
:errors-1
REM this is if it had an error:
ECHO Errors occurred.
goto exit
REM GUESS WHAT, THIS REM WILL NEVER EVER BE READ!  IT WILL BE SKIPPED OVER BY THE GOTOS
:exit
ECHO.
ECHO press any key to exit.
PAUSE>nul

The code is suppose to take 2 arguments, add them and echo the result.

But this won't execute with success on my Windows 8.1 machine. Below is what I get:

C:\ProjectDoc>add3.bat
Errors occurred.

press any key to exit.

So, U added an echo for the ERRORLEVEL to see its value after executing the command SET. Below is the output:

C:\ProjectDoc>add3.bat 2 3
9009
Errors occurred.

press any key to exit.
C:\ProjectDoc>

So, is this errorlevel in Windows equal to the $? of Linux. Should it be returning 0 for every successful execution of a command or is it different? Reading some docs relates it to the Linux $? but it isn't clearly working as $? in Linux.

Upvotes: 0

Views: 4832

Answers (1)

Klitos Kyriacou
Klitos Kyriacou

Reputation: 11621

Yes, to be precise, %errorlevel% is analogous to $? in Bash shell.

In your batch file, SET a=%1+%2 is not doing what you expect it to do. It just sets the value of the variable a to the string "2+3" assuming you ran the file with arguments 2 3. If you want to do arithmetic you need to use the /A option: set /a a=%1+%2.

The SET command (and many other built-in commands) only set the ERRORLEVEL if there has actually been an error. If it was successful, the ERRORLEVEL will retain its previous value. I think this is what you're witnessing in your question.

By contrast, when a command runs an executable file, when the process completes it always sets the ERRORLEVEL.

As well as checking the ERRORLEVEL variable for specific values, it is idiomatic (for historical reasons) to check the errorlevel using the following expression

IF ERRORLEVEL 1 ECHO Hello

This will run the given command if ERRORLEVEL is 1 or above - in other words, if any error has occurred.

Upvotes: 2

Related Questions