String Operations

Maintained on October 12, 2026

When writing batch files, you often need to process strings, for example to clean up file names or format log output.

Batch files have no dedicated string functions, but the special syntax of variable expansion lets you perform replacement, substring extraction, and concatenation.

Replacing Strings

To replace part of a string stored in a variable, use the following syntax.

set newvar=%variable:old=new%

Example

@echo off
setlocal

set TEXT=Hello World
echo Original: %TEXT%

set TEXT=%TEXT:World=Japan%
echo Replaced: %TEXT%

endlocal

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>replace.cmd

Original: Hello World

Replaced: Hello Japan

C:\users\user>

Converting Path Separators

set PATH_STR=C:\Users\user\Documents
set PATH_STR=%PATH_STR:\=/%
echo %PATH_STR%

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>echo %PATH_STR%

C:/Users/user/Documents

C:\users\user>

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Deleting Characters (Replacing with an Empty String)

set TEXT=  Hello
set TEXT=%TEXT: =%
echo [%TEXT%]

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>echo [%TEXT%]

[Hello]

C:\users\user>

Replacement Is Case-Insensitive

String replacement ignores case. %TEXT:hello=Hi% replaces Hello, HELLO, and hello alike.

Use * to delete everything up to and including a given string.

set TEXT=key=value
set VALUE=%TEXT:*==%
echo %VALUE%

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>echo %VALUE%

value

C:\users\user>

Characters You Cannot Replace

The string to be replaced cannot begin with =. Strings containing % or ! may also not be handled correctly by ordinary replacement.

Extracting Substrings

To extract part of a variable, use the following syntax.

%variable:~start,length%

Parameter	Description
start	Zero-based index
length	Number of characters to extract (to the end if omitted)
Negative value	Counts from the end of the string

Example

@echo off
setlocal

set TEXT=ABCDEFGHIJ

rem First 3 characters
echo %TEXT:~0,3%

rem 3 characters starting at the 4th (index 3 because it is zero-based)
echo %TEXT:~3,3%

rem Skip the first 2 characters
echo %TEXT:~2%

rem Last 3 characters
echo %TEXT:~-3%

rem Everything except the last 3 characters
echo %TEXT:~0,-3%

endlocal

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>substring.cmd

ABC

DEF

CDEFGHIJ

HIJ

ABCDEFG

C:\users\user>

Zero Padding

This example pads numbers to three digits.

@echo off
setlocal enabledelayedexpansion

for /L %%i in (1,1,5) do (
    set NUM=00%%i
    set NUM=!NUM:~-3!
    echo !NUM!
)

endlocal

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>zeropad.cmd

001

002

003

004

005

C:\users\user>

チェック

Zero padding is used frequently for sequential file names and log formatting. Prefix the number with zeros using set NUM=00%%i, then take the last three characters with !NUM:~-3!.

Concatenating Strings

In batch files, you can concatenate strings simply by writing variables next to each other.

@echo off
setlocal

set FIRST=Hello
set SECOND=World
set RESULT=%FIRST% %SECOND%
echo %RESULT%

endlocal

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>concat.cmd

Hello World

C:\users\user>

Building a String in a Loop

@echo off
setlocal enabledelayedexpansion

set RESULT=
for %%f in (*.txt) do (
    set RESULT=!RESULT! %%f
)

echo Files found:%RESULT%
endlocal

Getting the Length of a String

Batch files have no built-in way to get the length of a string. Instead, you can extract one character at a time and count until the result is empty.

@echo off
setlocal enabledelayedexpansion

set TEXT=Hello World
set LEN=0

:LOOP
if not "!TEXT:~%LEN%,1!"=="" (
    set /a LEN+=1
    goto LOOP
)

echo String: %TEXT%
echo Length: %LEN%

endlocal

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>strlen.cmd

String: Hello World

Length: 11

C:\users\user>

Using a Variable for the Position

You cannot write %TEXT:~%LEN%,1% when the start position or length is a variable. As in the example above, enable enabledelayedexpansion and write !TEXT:~%LEN%,1!. See the delayed expansion guide for details.

Things to Keep in Mind

Assign values with set "VAR=value". In set TEXT=abc a trailing space becomes part of the value. Wrapping the assignment in quotes, as in set "TEXT=abc", excludes any spaces outside the quotes.
A start position beyond the string length returns an empty result. When counting from the end, as in %TEXT:~-3%, a string shorter than 3 characters is returned in full.
There is no case-conversion feature. If you need one, consider combining for with replacement, or use PowerShell.
Replacement and substring extraction give unexpected results on undefined variables. Check first with if defined VARNAME.

Working with File Paths

In batch files, the for variable modifiers let you extract each part of a file path.

@echo off
set FILE=C:\Users\user\Documents\report.txt

for %%F in ("%FILE%") do (
    echo Full path:      %%~fF
    echo Drive:          %%~dF
    echo Folder:         %%~pF
    echo File name:      %%~nF
    echo Extension:      %%~xF
    echo Name + ext:     %%~nxF
)

－ □ ×

Command Prompt

Microsoft Windows [Version xx.x.xxxxx.xxx]

C:\users\user>path_parts.cmd

Full path: C:\Users\user\Documents\report.txt

Drive: C:

Folder: \Users\user\Documents\

File name: report

Extension: .txt

Name + ext: report.txt

C:\users\user>

Modifier	Description
`~f`	Full path
`~d`	Drive letter
`~p`	Path (folder part)
`~n`	File name without extension
`~x`	Extension
`~nx`	File name with extension

Summary

Operation	Syntax
Replace a string	`%variable:old=new%`
Extract a substring	`%variable:~start,length%`
Extract from the end	`%variable:~-length%`
Concatenate strings	`set RESULT=%A%%B%`
Delete everything before a string	`%variable:*string=%`