This example checks for the existence of the environment variable "VARIABLE." If VARIABLE does not exist, the statement is true and control of the batch file jumps to the MODULE section. If the statement is not true, that is, the VARIABLE variable does exist, program control skips to the next line of the batch file and continues.
IF "%VARIABLE%" == "" GOTO MODULE
NOTE: The quotation marks are necessary only when a variable is used in a logical IF statement.
The following example illustrates the use of the PATH environment variable within a batch file:
This example tests for the existence of the PATH variable. If it exists, control passes to the YESPATH section; otherwise, control is passed to the NOPATH section.
IF "%PATH%" == "" GOTO NOPATH
@ECHO The PATH environment variable was detected.
@ECHO The PATH environment variable was NOT detected.
If a path is detected and control is passed to the YESPATH section, C:\DOS is added to the existing path by using the %PATH% variable.