DoS - Error Level

Errorlevel is a system variable in Bash that contains the status or error code of the last command execution.

If it returns 0, the command is successful. If it returns non-zero, the command failed with an error, returns an exit(error) code.

For example,

@echo off
REM error level failed and succesfull case
ls
echo %errorlevel%

dir
echo %errorlevel%

We have used two commands in the batch script:

• ls is not a valid command in DOS and throws an error “ls command is not internal or external”, so errorlevel returns 9009.
• dir is a valid command and executes successfully, so it returns errorlevel as 0.

Batch IF Conditional checking Error Level Example

You can use the errorlevel variable in conditional expressions to execute conditional branches based on error or successful command execution.

To check the errorlevel, use the equ operator to check if the exit code is zero for successful operation.

@echo off
ls
echo %errorlevel%
if %errorlevel% equ 0 (
    echo Success.
) else (
    echo Failed. Errorlevel: %errorlevel%.
)

Batch File Error Codes

Errorlevel always returns an error code in a batch file. It is also called an exit code.

Errorlevel and ERRORLEVEL are the same.

These variables are not changed by the user, not recommended.