Batch Files - Error Handling

Question

I'm currently writing my first batch file for deploying an asp.net solution. I've been Googling a bit for a general error handling approach and can't find anything really useful.

Basically if any thing goes wrong I want to stop and print out what went wrong.

Can anyone give me any pointers?

Answer 1

I generally find the conditional command concatenation operators much more convenient than ERRORLEVEL.

yourCommand && (
  echo yourCommand was successful
) || (
  echo yourCommand failed
)

There is one complication you should be aware of. The error branch will fire if the last command in the success branch raises an error.

yourCommand && (
  someCommandThatMayFail
) || (
  echo This will fire if yourCommand or someCommandThatMayFail raises an error
)

The fix is to insert a harmless command that is guaranteed to succeed at the end of the success branch. I like to use (call ), which does nothing except set the ERRORLEVEL to 0. There is a corollary (call) that does nothing except set the ERRORLEVEL to 1.

yourCommand && (
  someCommandThatMayFail
  (call )
) || (
  echo This can only fire if yourCommand raises an error
)

See Foolproof way to check for nonzero (error) return code in windows batch file for examples of the intricacies needed when using ERRORLEVEL to detect errors.