What Is Error Handling?

Error handling means detecting when something goes wrong (missing file, wrong path, failed command) and reacting to it without crashing the script.

Check If a File Exists

if exist "data.txt" (
  echo File found!
) else (
  echo File missing!
)
      

Errorlevel Basics

Every command sets a special number called errorlevel. 0 = success Non-zero = failure

command
echo %errorlevel%
      

Using Errorlevel to Detect Failures

copy file1.txt backup.txt
if errorlevel 1 (
  echo Copy failed!
) else (
  echo Copy successful!
)
      

Important Note

IF ERRORLEVEL checks “greater or equal”, not equals.

if errorlevel 1 echo Something went wrong
if errorlevel 0 echo Everything OK
      

Safer Number Comparison

if %errorlevel%==0 (
  echo OK
) else (
  echo Error!
)
      

Try/Catch Style (Manual)

Batch doesn't have real try/catch, but you can simulate it:

@echo off

set "errorFlag=0"

copy missing.txt test.txt || set errorFlag=1

if %errorFlag%==1 (
  echo Copy failed!
) else (
  echo Success!
)
      

The Double-Pipe Trick

Command || fallback Runs fallback only if the first command fails.

mkdir testfolder || echo Folder could not be created!
      

The AND Trick

Command && next Runs next only if the first command succeeds.

echo Creating backup... && copy a.txt b.txt
      

Full Example — Safe Delete

@echo off

set "file=test.txt"

if not exist "%file%" (
  echo File does not exist!
  exit /b
)

del "%file%" && echo Deleted successfully! || echo Could not delete!
      

Why Error Handling Matters

• Prevents crashes
• Detects missing files
• Makes tools reliable
• Gives users better feedback

What’s Next?

Next you’ll learn how to work with Python lists and tuples — two of the most important data structures.