Performs conditional processing in batch programs. IF NOT ERRORLEVEL number command IF NOT string1=string2 command IF NOT ...

Performs conditional processing in batch programs.

IF [NOT] ERRORLEVEL number command
IF [NOT] string1==string2 command
IF [NOT] EXIST filename command

  NOT               Specifies that Windows should carry out
                    the command only if the condition is false.

  ERRORLEVEL number Specifies a true condition if the last program run
                    returned an exit code equal to or greater than the number
                    specified.

  string1==string2  Specifies a true condition if the specified text strings
                    match.

  EXIST filename    Specifies a true condition if the specified filename
                    exists.

  command           Specifies the command to carry out if the condition is
                    met.  Command can be followed by ELSE command which
                    will execute the command after the ELSE keyword if the
                    specified condition is FALSE

The ELSE clause must occur on the same line as the command after the IF.  For
example:

    IF EXIST filename. (
        del filename.
    ) ELSE (
        echo filename. missing.
    )

The following would NOT work because the del command needs to be terminated
by a newline:

    IF EXIST filename. del filename. ELSE echo filename. missing

Nor would the following work, since the ELSE command must be on the same line
as the end of the IF command:

    IF EXIST filename. del filename.
    ELSE echo filename. missing

The following would work if you want it all on one line:

    IF EXIST filename. (del filename.) ELSE echo filename. missing