errorlevel

ERRORLEVEL is a special value used in the Windows command line and batch scripting to capture the exit status returned by the last executed program. It is not a conventional environment variable you assign with SET; instead, the command interpreter updates ERRORLEVEL with the exit code produced by the previous command. This value is then used to control program flow in script logic, most often through conditional tests.

In batch files and CMD, the common way to test ERRORLEVEL is with the IF ERRORLEVEL n syntax. This form evaluates as true if the last command’s exit code is greater than or equal to n. Because the comparison is based on a threshold, scripts typically test higher values first to distinguish between multiple failure modes. For example:

- if errorlevel 3 echo severe error

- if errorlevel 2 echo moderate error

- if errorlevel 1 echo minor error

This descending order ensures the most specific condition fires correctly.

To check for an exact exit code, you can compare the numeric value directly using %ERRORLEVEL% (for example, if %ERRORLEVEL%==0 to detect success). Note that within a code block or loop, delayed expansion may be required to read ERRORLEVEL reliably, such as with !ERRORLEVEL!.

Common conventions associate 0 with success and nonzero values with failure or specific error conditions, but the exact meanings depend on the program that returned the code. ERRORLEVEL thus serves as a generic mechanism to propagate and respond to a program’s exit status in Windows batch automation.