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06-UserInputs-Arguments.md

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🎯 Positional Parameters (%1, %2, ..., %9)

  • When building command-line batch scripts, you often want to pass input arguments to the script — just like passing parameters to a function.

    That’s where positional parameters (%1 through %9) come in.

    📌 What Are Positional Parameters?

    In batch scripting, %1, %2, ..., %9 refer to the arguments passed to your script from the command line or when calling one batch file from another.

    Each %n holds the nth argument:

    :: call like:
myscript.bat arg1 arg2 arg3

:: inside myscript.bat
ECHO First argument is %1
ECHO Second argument is %2

    📂 How to Use: The Basics

    🔹 Script: greet.bat

    @ECHO OFF
ECHO Hello, %1!

    🔹 Run it:

    greet.bat Alice

    ✅ Output:

    Hello, Alice!

📊 Positional Parameter

  1. 📝 Example 1: Multiply Two Numbers

    :: multiply.bat
@ECHO OFF
SET /A result=%1 * %2
ECHO %1 x %2 = %result%
    multiply.bat 6 9

    ✅ Output:

    6 x 9 = 54

  2. 📝 Example 2: Rename a File

    :: renamefile.bat
@ECHO OFF
IF EXIST "%1" (
    REN "%1" "%2"
    ECHO Renamed %1 to %2
) ELSE (
    ECHO File %1 not found!
)
    renamefile.bat oldname.txt newname.txt

  3. 📝 Example 3: Backup with Timestamp

    :: backup.bat
@ECHO OFF
SET filename=%1
COPY "%filename%" "%filename%_%DATE:/=-%.bak"
    backup.bat config.json

    ✅ Creates something like:

    config.json_2025-07-22.bak

🚨 Gotchas & Limitations

Issue Explanation / Fix
Only %1 to %9 available No %10, %11 etc — %10 is interpreted as %1 + 0
Use SHIFT for more params SHIFT lets you access beyond 9 (see below)
Quoting required for spaces Always quote: "My File.txt"

🔄 Accessing More than 9 Parameters: SHIFT

  • When you need to handle more than 9 arguments, use the SHIFT command to rotate the arguments left by 1.

    🔹 Example: Show All Arguments One by One

    @ECHO OFF
:loop
IF "%1"=="" GOTO end
ECHO Arg: %1
SHIFT
GOTO loop
:end
    loopargs.bat one two three four five six seven eight nine ten eleven

    ✅ Output:

    Arg: one
Arg: two
...
Arg: eleven

🧠 Bonus: Argument Validation

@ECHO OFF
IF "%1"=="" (
    ECHO Usage: %0 filename
    EXIT /B 1
)

This pattern:

  • Checks if %1 is missing
  • Shows usage and exits cleanly

🧪 Example: Forward All Parameters with %*

:: wrapper.bat
@ECHO OFF
ECHO Calling inner script with: %*
CALL inner.bat %*

%* means: “all arguments as one string”.

🧼 Best Practices

Tip Why
Quote %1, %2 if file paths are involved Handles spaces in paths
Validate args before use Prevent errors or unexpected behavior
Use SHIFT in loops with many args Enables argument handling beyond %9
Use %~n1, %~x1, etc. for parsing Extract parts of filenames (see below)

🔍 Bonus: Parameter Modifiers

Expression Meaning
%~f1 Fully qualified path of %1
%~n1 File name only
%~x1 File extension only
%~dp1 Drive + path of %1 
:: Show parts of a file path
@ECHO OFF
ECHO File: %1
ECHO Name: %~n1
ECHO Extension: %~x1
ECHO Path: %~dp1

📝 Summary

Feature Description
%1–%9 Positional arguments to scripts
%* All arguments as one
SHIFT Shift all arguments left (access beyond %9)
Modifiers Extract filename, extension, path, etc.