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Conditional Logic: IF/ELSE

The IF command takes a test, and uses the result of the test to control the execution of one or more commands. An ELSE clause is optional; if included, the first conditional commands should be placed in parenthesis.​

> set A=Blue                                       ​
> set B=Orange​
> set C=Blue​
​> if %A%==%C% echo Strings A and C match​
Strings A and C match​
> if %A%==%B% (echo Same!) else echo Different!​
Different!

Available Tests​

There are four main types of tests available:

Tests Group 1: Filesystem Entries​

Tests that a filename exists (regardless of the entry type: file or directory):

EXIST filename

Tests Group 2: String Equality​

Test for string equality:

string1 == string2

Tests Group 3: String and Numeric Comparisons​

These tests accept two string arguments, both strings or both integers, which are compared. Adding the /i switch will make string comparisons case-insensitive (UPPER/lowercase).​

value1 EQU value2    True if the values are equal​
value1 NEQ value2    True if the values are not equal​
value1 LSS value2    True if the value1 less than value2 ​
value1 LEQ value2    True if the value1 less/equal to value2​
value1 GTR value2    True if the value1 greater than value2​
value1 GEQ value2    True if the value1 greater than or equal to to value2​

To force a string comparison, enclose value1 and value2 in quotes. Otherwise, the shell will determine if the variables appear to contain integer values and compare them as integers, or otherwise compare them as strings.

Tests Group 4: Variable Definition, Errorlevel​

Test to see if a variable is defined​: ​

DEFINED variable    True if variable is defined​

Test to see if the ERRORLEVEL is above a threshold​:

ERRORLEVEL value    True if ERORRLEVEL>=value​

Although it's probably better to just an integer comparison such as: %ERRORLEVEL% GEQ value​

Notes about IF and these Tests​

  • These tests work only with the IF command
  • The IF command can be used with GOTO and a label:
IF test GOTO :skip​
...​
:skip​

Note that using a GOTO in a loop will make the shell forget about the loop, regardless of where the label is located!​

Negating and Combining Tests​

You can negate (invert) a test with the NOT operator:

IF NOT EXIST %N% ECHO The file %N% does not exist.

Note that you cannot combine tests - there is no AND or OR operator -- but you can nest tests (which is similar to using AND).