Conditionally executes a command. Available elementary tests:

• exist <filename>
• <string>==<string>
• <expression1> equ <expression2> -- equals
• <expression1> neq <expression2> -- not equal
• <expression1> lss <expression2> -- less than
• <expression1> leq <expression2> -- less than or equal
• <expression1> gtr <expression2> -- greater than
• <expression1> geq <expression2> -- greater than or equal
• defined <variable>
• errorlevel <number>
• cmdextversion <number>

To each elementary test, "not" can be applied. Apparently there are no operators like AND, OR, etc. to combine elementary tests.

The /I switch makes the == and equ comparisons ignore case.

An example:

if not exist %targetpath% (
  echo Target path not found.
  exit /b
)

Examples:

• if not 1 equ 0 echo Not equal

• if 1 equ 0 echo A & echo B

  Does nothing; both echo commands are subject to the condition.

• if not 1 equ 0 goto :mylabel