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This article mainly explains "the example usage of dos if conditional judgment sentence". The content of the explanation in this article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn the example usage of dos if conditional judgment sentence.

1. To determine whether a drive, file or folder exists, use the if exist statement

2. To determine whether two strings are equal, use the if "string 1" = = "string 2" statement

3. To judge whether two values are equal, use if numerical value 1 equ numerical value 2 statement

4. To determine whether a variable has been assigned, use the if defined str statement

The complete format of the if statement is as follows: if conditional expression (statement 1) else (statement 2), which means that if the conditional expression holds, then statement 1 is executed, otherwise statement 2 is executed.

For the above four cases, you can use the following code:

1. If exist d:\ test.txt (test.txt exists under echo D) else (test.txt does not exist under echo D)

2. If "abc" = = "xyz" (echo string abc equals string xyz) else (echo string abc is not equal to string xyz)

3. If 1 equ 2 (echo 1 equals 2) else (echo 1 is not equal to 2)

4. If defined str (the echo variable str has been assigned to% str%) else (the value of the echo variable str is empty)

When judging whether a string is equal, if will be case-sensitive. For example, a simple if statement will think that the string abc is different from the string Abc. If you do not want to be case-sensitive, you need to add a / I switch, using the format of if / I "string 1" = = "string 2"; in addition, the equal symbol is a continuous "=" rather than a separate "=".

To judge the size relationship between two values, in addition to using equ, there are other relation symbols, all of which are applicable to if statements as shown in the following table:

Chinese meaning relation symbol English interpretation

Equal to equ equal

Greater than gtr greater than

Greater than or equal to geq greater than or equal

Less than lss less than

Less than or equal to leq less than or equal

Not equal to neq no equal

The if statement also has a simplified format: the if conditional expression statement, which means that if the conditional expression is valid, the statement will be executed, otherwise, nothing will be done.

Learning if conditional statements

Key points of study:

The basic syntax of five if statements:

one. To determine whether two strings are equal, if "string 1" = = "string 2" command statement

two. To determine whether two values are equal, if value 1 equ number 2 command statement

three. Determine whether a drive, file, or folder exists, if exist filename command statement

four. Determine whether the variable has been defined, if defined variable command statement

five. Determine the return value of the last command, the if errorlevel numeric command statement.

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one. To determine whether two strings are equal, if "string 1" = = "string 2" command statement

Note: in "string 1" = "string 2", there are two consecutive "="

Example 1

@ echo offset / p var1= Please enter the first comparison character: set / p var2= Please enter the second softer character: if "% var1%" = = "% var2%" (the two characters entered by echo are the same) the two characters entered by else echo are different pause

After execution, you will be asked to enter two strings, and then batch to determine whether the two are the same. When determining whether strings are equal, if is case-sensitive

Yes, please take a look

Example 2

@ echo offif "a" = = "A" (two characters entered by echo are the same) two characters entered by else echo are not the same pause

After execution, it will be displayed that the two characters entered are different.

If we don't want it to be case-sensitive, we can add the / I parameter. Take a look at the following example

Example 3

@ echo offif / I "a" = = "A" (two characters entered by echo are the same) two characters entered by else echo are not the same pause

After this execution, it will be displayed: the two characters entered are the same

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two. To determine whether two values are equal, if value 1 equ number 2 command statement

The equ in the statement means equality, and the following relation symbols are used to judge the size relationship between the two values:

Chinese meaning relation symbol English interpretation

Equal to equ equal

Greater than gtr greater than

Greater than or equal to geq greater than or equal

Less than lss less than

Less than or equal to leq less than or equal

Not equal to neq no equal

Let's look at an example.

Example 4

@ echo off set / p var= Please enter a number: if% var% geq 10 (echo is greater than or equal to 10) else echo this number is less than 10pause

Note that the greater than sign, less than sign, equal sign and so on in batch processing cannot be used: ">"

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