Dos - If

About

To get more help on the if statement, type on the command line prompt:

help if

Syntax

Statement

If Else

IF condition (
   command
   ) ELSE (
   command
   )

where:

• condition syntax is a condition

When using the else construct:

• The command needs to be terminated by a newline or the block command must be defined with brackets.
• The else statement must be in the same flow than the if

IF condition (command) ELSE command

Short If

IF condition command

Condition

text and number comparison

Syntax

[/I] [NOT] string1==string2

and

[/I] string1 compare-op string2

where

• the /I switch specify a case insensitive comparison.
• compare-op may be one of:
  • EQU - equal
  • NEQ - not equal
  • LSS - less than
  • LEQ - less than or equal
  • GTR - greater than
  • GEQ - greater than or equal

Example

• Text Comparison

@echo off
set hello=hello
if "%hello%"=="hello" echo %hello% world

hello world

• Number

if 2 GTR 1 (echo Yes) else echo No

Yes

exist

Syntax

[NOT] EXIST filename

where:

• the parts enclosed between bracket are optional (ie NOT)
• filename is the name of the file

Example

@echo off
if exist hello.bat (
    echo hello.bat exist
    )

hello.bat exist

Errorlevel

Without comparison

Syntax:

ERRORLEVEL number 

This condition will return a true condition if the last program run returned an exit code (Errorlevel) equal to or greater than the number specified. When a command executes without error it terminates with an exit status of zero.

With comparison

With the string comparison

[NOT] %ERRORLEVEL% [compare-op]  number 

where:

• %ERRORLEVEL% is the dynamic variable of ERRORLEVEL
• compare-op can be one of the following
  • EQU - equal
  • NEQ - not equal
  • LSS - less than
  • LEQ - less than or equal
  • GTR - greater than
  • GEQ - greater than or equal

See Error level example

Defined

Syntax:

[NOT] DEFINED variableName

Example:

if not defined v (echo v is not defined) else echo %v%

v is not defined

set v=Call Me Nico
if not defined v (echo v is not defined) else echo %v%

Call Me Nico

Support

was unexpected at this time.

This error occurs really often when you test a condition over a variable that is not set.

The command interpreter first replace the variable with its value before starting the command and the result is an error in the syntax as the variable has no value.