Introduction to Windows Batch Commands and Scripting

Recently I needed to automate configuration tasks on a Windows virtual machine using BAT commands, so I studied batch scripting and prepared this introductory guide.

Batch commands are DOS/Windows scripts with the .bat extension; they include a set of symbols and commands divided into three categories, which are introduced below.

Common file and system commands: Dir (list files), md (make directory), cd (change directory), copy (copy files), del (delete files), ren (rename), type (display file content), format (format disk), discopy (duplicate disk), deltree (delete directory tree), mem (show memory), chkdsk (check disk), cls (clear screen), time (show system time), date (show system date), var (show OS version).

Typical batch programming commands: PAUSE to halt execution ("Press any key to continue"), echo %errorlevel% to view the return code, CALL to invoke another batch file, and setlocal enabledelayedexpansion for delayed variable expansion. The following examples illustrate variable behavior with and without delayed expansion:

@echo off
set a=4
set a=5 & echo %a%
pause

Output is 4 because %a% is expanded before the second assignment. With delayed expansion:

@echo off&setlocal enabledelayedexpansion
set a=4
set a=5 & echo !a!
pause

Now the output is 5.

Variable assignment (SET) examples:

set var=123
echo %var%
set /p var=请输入你的名字   ; /p prompts for input
set /a var=3-1   ; /a evaluates arithmetic expression

Conditional statements (IF): checking existence (if exist d:\test.txt), string equality (if "abc"=="xyz"), numeric equality (if 1 equ 2), and defined variables (if defined str).

FOR loop syntax: FOR %%variable IN (set) DO command [command-parameters] with parameters /d (directories), /r (recursive), /l (numeric range), /f (file/content parsing). Example usages:

@echo off
for /d %%i in (*) do @echo %%i
pause

Lists all sub‑directories.

@echo off
for /r c: %%i in (*.exe) do @echo %%i
pause

Recursively lists all .exe files on C:.

@echo off
for /l %%i in (1,1,5) do @echo %%i
pause

Prints numbers 1 through 5.

File‑content parsing examples:

for %%i in (a.txt) do echo %%i          ; show file name
for /f %%i in (a.txt) do echo %%i          ; show each line
for /f "delims= " %%i in (a.txt) do echo %%i   ; first column
for /f "tokens=2 delims= " %%i in (a.txt) do echo %%i   ; second column
for /f "tokens=2,3 delims= " %%i in (a.txt) do echo %%i %%j   ; second and third columns

Batch script parameters: %0, %1 … %9, %* represent the script name and arguments passed from the command line.

Common batch symbols: @ and echo for output control, redirection operators (> , >> , <), pipe (|), escape (^), logical operators (&, &&, ||), variable syntax (%%, %CD%, %DATE%, %HOMEPATH%, %PATH%), and comment markers (:: and REM).