5. Conditionals with `if`¶

What & why¶

if is how a script makes decisions. Batch's if is limited and quirky: string comparison is the default, quoting matters enormously, and there are special forms for files, variables and exit codes.

String comparison¶

@echo off
set "answer=yes"

if "%answer%"=="yes" (
    echo Confirmed.
) else (
    echo Cancelled.
)

Always quote both sides. If answer is empty, if %answer%==yes becomes if ==yes → The syntax of the command is incorrect. Quoting makes it if ""=="yes" → cleanly false.

== is the only string operator with that spelling. There is no !=; negate with if not:

if not "%answer%"=="yes" echo Not yes.

Case-insensitive¶

if /i "%answer%"=="YES" echo Matches regardless of case.

Numeric comparison¶

set /a count=5
if %count% GEQ 3 echo At least three.

Operator	Meaning
`EQU`	equal
`NEQ`	not equal
`LSS`	less than
`LEQ`	less than or equal
`GTR`	greater than
`GEQ`	greater than or equal

Warning

These do a numeric comparison only when both sides look like numbers; otherwise they fall back to string comparison. if "10" GTR "9" is true numerically, but if "10" GTR "9 " (trailing space) compares as strings and is false. Keep both sides clean and unquoted for numeric intent: if %a% LSS %b%.

`if exist` — files and folders¶

if exist "C:\logs\app.log" echo The log exists.
if not exist "%~dp0config.ini" (
    echo Missing config next to script.
    exit /b 1
)

rem A trailing \ tests for a directory specifically:
if exist "C:\logs\" echo C:\logs is a folder.

if exist "folder\*" is another way to test a non-empty folder.

`if defined` — variables¶

if defined USERPROFILE echo Profile: %USERPROFILE%
if not defined MYVAR echo MYVAR is not set.

Use if defined instead of if "%var%"=="" — it's cleaner and it works with delayed expansion (if defined arr[%i%]).

`if errorlevel` — exit codes¶

ping -n 1 example.com >nul
if errorlevel 1 (
    echo Ping failed.
) else (
    echo Ping succeeded.
)

if errorlevel N means "exit code is N or greater." So if errorlevel 1 catches any failure. To test for exactly one value, use %errorlevel%:

if %errorlevel% equ 0 echo Exactly zero.

Check them in order high-to-low if you branch on several:

if errorlevel 2 ( echo code ^>= 2 ) else if errorlevel 1 ( echo code == 1 ) else ( echo code == 0 )

Blocks, `else`, and the parenthesis trap¶

The else must be on the same line as the closing ):

if "%x%"=="1" (
    echo one
) else (
    echo not one
)

This is a syntax error:

if "%x%"=="1" (
    echo one
)
else (            REM  <-- "else" was unexpected at this time
    echo not one
)

Inside ( ... ) blocks, %var% is expanded once, when the block is parsed — not as it runs. This breaks counters and loop bodies. The fix is delayed expansion, Intermediate Lesson 1. For now, keep if blocks simple.

Chaining conditions¶

There is no if A and B. Nest, or use flags:

if "%user%"=="admin" if "%mode%"=="write" echo Allowed.

rem "or" via a helper flag:
set "ok="
if "%ext%"==".jpg" set "ok=1"
if "%ext%"==".png" set "ok=1"
if defined ok echo It's an image.

Common mistakes¶

Unquoted comparison with a possibly-empty value → syntax error.
else on its own line → else was unexpected at this time.
if errorlevel 0 is always true (every code is ≥ 0). Use if %errorlevel% equ 0 or if not errorlevel 1.
== with surrounding spaces: if "%x%" == "y" — the spaces become part of neither side here, that's actually fine, but if %x%==%y% without quotes and with spaces around values is not. Prefer quoted, no spaces around ==.
if /i position: the /i goes right after if, before the first operand.
Testing a directory with if exist name — works, but add a trailing \ to be sure it's a folder not a file.

Exercises¶

Prompt for a password; if it equals hunter2, print Access granted, else Access denied and exit /b 1.
Accept a number as %1. Print whether it is negative, zero, or positive using LSS/EQU/GTR.
Check whether %~dp0notes.txt exists; if not, create it with echo.>"%~dp0notes.txt" and print Created.
Accept %1; if it's empty, print usage and exit /b 1; if /i equal to --help, print help; otherwise echo it back.
Run findstr xyz nul (which fails), then branch on if errorlevel 1.
FizzBuzz for %1: use set /a and if with %% to print Fizz, Buzz, FizzBuzz, or the number.

Recap¶

Quote both sides: if "%a%"=="%b%". Negate with if not. Case-insensitive with if /i.
Numeric: EQU NEQ LSS LEQ GTR GEQ — keep operands clean numbers.
if exist "path" (trailing \ for folders), if defined VAR, if errorlevel N (means ≥ N).
else sits on the ) line. %var% inside ( ) is expanded at parse time — a real gotcha.

Next: Loops with for →

5. Conditionals with if¶