If/Else in Batch

The if command in batch files compares values and branches execution, with the general form if condition (command) else (command). String comparisons use if %VAR%==value, and because batch has no true boolean type, comparisons are done on text unless you add the /i switch for case-insensitive matching. A crucial syntax rule is that the else clause must appear on the same line as the closing parenthesis of the if block, or the interpreter will not recognize it as belonging to that if.

For numbers, if supports comparison operators like EQU, NEQ, LSS, LEQ, GTR, and GEQ, as in if %SCORE% GEQ 50 (echo Pass), which correctly handles numeric magnitude instead of string ordering. Batch can also test the filesystem directly: if exist file.txt (...) checks for a file's presence, and if not exist folder\ (...) checks for its absence, both without needing an external command. These file tests are commonly combined with del, copy, or mkdir to build scripts that safely handle missing files or directories.

File existence checks let a script adapt to its environment without crashing: if exist config.ini (call :LoadConfig) else (call :CreateDefaultConfig) avoids errors from trying to read a file that was never created. Directory checks work the same way, though a trailing backslash such as if exist logs\ (...) is a common convention for checking specifically for a directory rather than a same-named file. Combining if exist with del prevents the classic 'Could not find file' error message that appears when deleting something that is not actually there.

Every command sets an errorlevel, a numeric exit code where 0 conventionally means success and any nonzero value signals failure; check it with if errorlevel 1 (...), which actually matches any errorlevel greater than or equal to 1, not exactly 1. This is how scripts detect whether a previous command like xcopy or ping succeeded before proceeding. if blocks can be nested inside each other to express multiple conditions, though deeply nested parentheses become hard to read and are often better refactored into labeled subroutines called with call.