Batch processing command instruction if statement _dos/bat

If is used for conditional judgment, it applies to the following scenarios:

1, to determine whether the drive, file or folder exists, with if exist statement;
2, to determine whether the two strings are equal, with the If "string 1" = "string 2" statement;
3, to determine whether the two values are equal, using the IF value 1 equ value 2 statements;
4, to determine whether a variable has been assigned value, using if defined STR statement;

The full format of the IF statement is this: if conditional expression (statement 1) Else (statement 2), which means that if the conditional expression is set up, then the statement 1 is executed, otherwise the statement 2 is executed.

For each of the above four scenarios, you can use the following code:

1. If exist D:\test.txt (Test.txt exists under echo D disk) Else (test.txt not present under Echo D disk)
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 (echo variable str has been assigned a value of%str%) else (the value of echo variable str is null)

When judging whether strings are equal, if the case is case-sensitive, for example, the simple if statement will assume that the string ABC is not the same as the string ABC, and if you do not want to be case-sensitive, you need to add the/I switch, using the if/i "string 1" = "string 2" format; Rather than a separate "=".

To determine the size relationship between two values, in addition to being equal to equ, there are other relationship symbols, and all the relationship symbols that apply to if statements are shown in the following table:

Chinese meaning	Relationship characters	English explanation
Equals	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 not equal to	Leq	Less than or equal
Not equal to	Neq	No equal

The IF statement also has a thin format: an If conditional expression statement, which means that if a conditional expression is set up, the statement is executed, otherwise, nothing is done.

Examples of multiple-layer if nested syntax:

If exist a.txt (
  if exist 1.txt (
    echo exists a.txt and 1.txt
  ) Else (
    Echo exists a.txt but does not exist 1. txt
  )
) Els E if exist b.txt (
  echo does not exist a.txt but exists b.txt
) Else (
  Echo does not exist a.txt and b.txt
)

The above mentioned is the entire content of this article, I hope you can enjoy.