Check if a file exists from inside a batch file

In case of checking file inside a batch file, you can simply check by file exist as following:

if exist {insert file name here} (
    rem file exists
) else (
    rem file doesn't exist
)

If you want to implement it by single line, you can implement it as following:

if exist {insert file name here} {action}

And following is the practical example:

if exist c:autoexec.bat notepad c:autoexec.bat