what does > nul 2>&1 mean in a batch statment

Question

I currently have a batch statement that looks like this

findstr \"PreprocessorDefinitions=.*%D_KEYWORD%\" %PROJ% > nul 2>&1
if errorlevel 1 (
    set D         


        

Answer 1

Don't use a piping operator, which is what ">" is.

All programs have three streams:

• Standard Input (the input from the console)
• Standard Output (general logging/UI output to the console)
• Standard Error (logging/UI output to the console meant for error messages or other exceptional behavior)

command >nul

^ This says to pipe the standard-output stream to null.

command 2>nul

^ This says to pipe the standard-error stream to null.

command 2>&1

^ This says to pipe the standard-error stream to the same place as the standard-output stream.