Correct Testing Precedence of Batch File ERRORLEVELs (39585)

SUMMARY

When you use multiple IF ERRORLEVEL statements in batch files, the order in which the ERRORLEVELs are tested numerically is important. The correct order is descending (highest to lowest). This ordering is from the way ERRORLEVELs are tested. The IF condition is set to TRUE when the ERRORLEVEL is equal to, or greater than, the ERRORLEVEL number.

MORE INFORMATION

The following batch file fragment demonstrates this INCORRECT behavior:

   rem (execute a program which returns an errorlevel of 0 or 1)
   if errorlevel 0 goto ZERO
   if errorlevel 1 goto ONE
   goto END
   :ZERO
     echo a Zero was returned!
     goto END
   :ONE
     echo a One was returned!
   :END

The above example always branches to the "ZERO" label, regardless of success or failure. This example would work correctly if the ERRORLEVEL testing was made in descending order.

The CORRECT way to write such a batch file is as follows:

   rem (execute a program which returns an errorlevel of 0 or 1)
   if errorlevel 1 goto ONE
   if errorlevel 0 goto ZERO
   goto END
   :ZERO
     echo a Zero was returned!
     goto END
   :ONE
     echo a One was returned!
   :END