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Windows batch file variable scope

I think this is a question about variable scope. It isn't, though. Command scripts don't have the notion of scopes for variables. What you are encountering is the well known and decades-old1 problem of variable substitution in a compound command preceding the part of that compound command that sets the variable to a new value. One can see exactly the same thing occurring with a simple two-liner: set A=ONE set A=TWO & echo %A% The variable expansion on the second line, which is a compound command, occurs when the command is parsed, which happens before any part of it is executed in Microsoft's (and IBM's, and indeed my) command interpreters. Your for command is one multiple line compound command. Microsoft's CMD has delayed variable expansion, which isn't enabled by default and one has to enable (with the /v:on command-line option to the command interpreter or via the EnableDelayedExpansion option to the setlocal command in a command script), to combat this: set A=ONE set A=TWO & echo !A! JP Software's TCC takes a different tack, and expands variables in compound commands progressively, processing each simple command within the compound as it reaches it. So it doesn't expand the %A% in the preceding examples until after it has executed the second set command. 1 The first command interpreter to exhibit this, if memory serves, was cmd in OS/2 version 1.0, released in 1987. This was Microsoft's first command interpreter that supported compound commands. The batch script also supports the concept of the variable similar to the other programming language. In this article, you will see how we can create a batch file variables and how we can use it. In the batch file, we can create variable two types, one is using the set commands and another is for the parameters which can be passed when the batch file is called. First I will describe how we can create a variable using the set command. You can see, Batch file commands SET If used set command without parameters, it displays the current environment variable settings. We can also create a variable or overwrite any existing variable using the set command. Syntax, Assigning a string set Variable_Name=Variable_Value Assigning a numeric value set /a Variable_Name=Numeric_Value Getting value from a user and assigning it to the variable. set /p Variable_Name=Line_input_User You can see, how to create a batch file. Let see few examples, In the bellow batch script, I am creating a variable Blog and storing a string Aticleworld. After storing the string I am displaying it on the console. @echo OFF SET Blog=Aticleworld Rem ***displaying Blog name*** ECHO %Blog% There should not space between the variable name and the equal sign (=). @echo OFF SET Blog = Aticleworld Rem ***displaying Blog name*** ECHO %Blog% In the bellow batch script, I am creating a variable year (numeric variable) to store the years and displaying the value on the console. @echo OFF SET /a year=1991 Rem ***displaying year*** ECHO %year% In the bellow batch script, I am creating a variable var to get the value from the user and displaying it on the console. @echo OFF echo Enter value SET /p var= echo value is ECHO %var% Batch program to add two batch file variables @echo off SET /A a = 6 SET /A b = 27 SET /A c = %a% + %b% echo %c% Code Analysis: I have created two variables a and b and store 6 and 27 respectively. Adding the value of a,b, and store it in c. Now, displaying the value of the c. Variable Scope (Global vs Local) By default the scope of the variable in a batch file is global. It means if you will create a variable in the batch file that it can be accessed anywhere in the program. Local variables have a defined boundary in which only they can be accessed. In the batch script, we can create a local variable using the SETLOCAL command. The scope of the local variable only between the SETLOCAL and ENDLOCAL command and it is destroyed as soon as the ENDLOCAL statement is executed. See the below example, In the below batch script, I am creating two variable one is global (var1) and another one is local (var2). @echo oFF rem it a is global variable SET var1=global rem it a is global variable SETLOCAL SET var2=local rem display local variable ECHO %var2% ENDLOCAL rem display global variable ECHO %var1% PAUSE So you can see in this output, you able to access both local and global variables and echo is printing their value. Now let's see what happens when we try to use a local variable beyond its scope which means try to access the local variable after ENDLOCAL. @echo oFF rem it a is global variable SET var1=global rem it a is global variable SETLOCAL SET var2=local ENDLOCAL rem display local variable ECHO %var2% rem display global variable ECHO %var1% PAUSE So you can see in this output when you try to access the local variable beyond its scope, the ECHO is turned off. Command Line Arguments in Batch file The batch file can read the command-line argument with a special syntax. If you want to read the command line arguments you need to write % with command line argument position. Suppose if you want to read the 1st argument of the command line, you need to write %1 in the batch file. Let see example code, Below batch file accept three command-line arguments and displaying it on the console using the echo. @echo oFF echo %1 echo %2 echo %3 PAUSE Recommended Articles for you: Declaring variables with the "set" command and their use is discussed. Variables have a core place in many scripting languages but play a lesser role in the Windows command line. Many commands are predefined and the scope of variables is rather limited. Nonetheless, there are important applications of the command line where variables must be employed and in this article I will outline how the command line uses variables. In one sense, there are two categories of variables for the command line. Some might use the term "variable" for the placeholders or arguments %1, %2, ..%9, that are used to represent user input in batch files. (See the discussion on this page.) However, the term "variable" is normally reserved in command line usage for entities that are declared as environment variables with the "set" command. Note that this is a pretty primitive way to define variables. For example, there is no typing. Environment variables, including numbers, are stored as strings and operations with them have to take that into account. Variables are declared and given a value in a single statement using "set". .The syntax is: set some_variable = some_valueVariable names are not case-sensitve and can consist of the usual alphanumeric and other common characters. Some characters are reserved and have to be escaped. They should be avoided. These include the symbols in Table II on this page. Also, since these are environment variables, their names should be enclosed in percent signs when used in references and expressions, e.g, %some_variable%. The percent signs are not used in the left side of the set statement that declares a variable. Localizing variables The declaration of a variable lasts as long as the present command window is open. If you are using a batch file that does not close its instance of the command window when the batch file terminates, any variables that the batch file declares remain. If you wish to localize a variable to a particular set of statements, use the "setlocal" and "endlocal" commands. Thus. to confine a variable declaration to a particular block of code, use:....setlocal set some_variable = some_value...some statements endlocal... Variables from user input The "set" command can also accept input from a user as the value for a variable. The switch "/p" is used for this purpose. A batch file will wait for the user to enter a value after the statement set /p new_variable= When the user has entered the value, the script will continue. A message string to prompt for input can also be used. For example:set /p new_variable="Enter value "Note the space at the end of the prompt message. Otherwise, the prompt message and the user-entered value will run together on the screen. It works but it looks funny. The user may be tempted to hit the spacebar, which adds a leading space to the input value. Arithmetic operations The command line is not designed for handling mathematical functions but it is possible to do some very simple integer arithmetic with variables. A switch " /a" was added to the "set" command to allow for some basic functions. Primarily, the use is adding and subtracting. For example, it is possible to increment or decrement counters in a loop. In principle, it is also possible to do multiplication and division.but only whole numbers can be handled so the practical use is limited. Although variables are stored as strings, the command interpreter recognizes strings that contain only integers, allowing them to be used in arithmetic expressions. The syntax is set /a some_variable={arithmetic expression}The four arithmetic operators are shown in Table I. (I have omitted a "modulus" operation, which uses the % sign in yet another way. In my opinion this just adds difficulty to an already quirky syntax. Using % in more than one sense can only confuse.) Symbol Operation + Addition - Subtraction * Multiplication / Division Here is an example of a variable %counter% being incremented:set /a counter=%counter%+1This can also be written as:set /a counter+=1 Variables in comparison statements in batch files Variables are often used in comparisons in conditional statements in batch files. Some of the comparison operators that are used are given in Table I of the page on "If" statements. Because of the somewhat loose way that the command line treats variables, it is necessary to be careful when comparing variables. For strings, the safest way is to quote variables. For example: if "%variable1%" == "%variable2%" some_commandBack to top

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