IF

Performs conditional processing in batch programs. If the condition
specified by an IF command is true, MS-DOS carries out the command that
follows the condition. If the condition is false, MS-DOS ignores the
command. You can use this command only in batch programs.

Syntax

    IF [NOT] ERRORLEVEL number command

    IF [NOT] string1==string2 command

    IF [NOT] EXIST filename command

Parameters

NOT
    Specifies that MS-DOS should carry out the command only if the condition
    is false.

ERRORLEVEL number
    Specifies a true condition only if the previous program run by
    COMMAND.COM returned an exit code equal to or greater than number.

command
    Specifies the command that MS-DOS should carry out if the preceding
    condition is met.

string1==string2
    Specifies a true condition only if string1 and string2 are the same.
    These values can be literal strings or batch variables (%1, for
    example). Literal strings do not need quotation marks.

EXIST filename
    Specifies a true condition if filename exists.