batch-fileFile Handling in batch files

Introduction

In this topic you will learn how to create, edit, copy, move, and delete files in batch.

Creating a File in Batch

There may be multiple reason why you want to create a text file in batch. But whatever the reason may be, this is how you do it.

If you want to overwrite an existing text file use >. Example:

@echo off
echo info to save > text.txt

But if you want to append text to an already existing text file use >>. Example:

@echo off
echo info to save >> text.txt

If you need to save multiple lines of text to a file use ()>text.txt Example:

@echo off
(echo username
 echo password)>text.txt

How to Copy Files in Batch

You may want to copy files from one place to another. In this example we'll teach you.

You can use the command xcopy. The syntax is xcopy c:\From C:\To

Example:

@echo off
xcopy C:\Folder\text.txt C:\User\Username\Desktop

There are also switches you can use. If you want to view them open up command prompt by Start Menu -> Accessories -> Command Prompt and then type xcopy /?

Moving Files

Using the move command, you can move files:

@echo off
cd C:\Foo\Bat\Baz
move /Y Meow.bat "Meow Folder" >nul

Meow.bat stands for which file to move. The "Meow Folder" moves Meow.bat to the Meow Folder. /Y says to not prompt for confirmation. Replacing that with /-Y makes the batch file prompt for confirmation. The >nul hides the command output. If it didn't have >nul, it would output:

    1 File Moved

Deleting Files

Using the DEL(alias for ERASE) command, one can remove files.

@echo off
del foo.ext

This command will delete foo.ext from the current directory. One can also specify path and file, such as:

del C:\Foo\Bar\Baz.ext

But it is always ideal to put quotes (") around paths, see here for the reason.


There are a few flags available for DEL.

FlagFunction
/PPrompts user before deleting file(s)
/FForcefully remove read-only file(s)
/SRemove file(s) in subdirectories
/QPrevents the user prompt
/AFilter: Only remove specific attributed file,
using the - character means not attributed as that type.

Copy Files Without xcopy

In this example, user BoeNoe showed how to use the command xcopy to copy files. There is also an extra command called copy.

Here is a simple example:

copy foo.ext bar.ext

This copies foo.ext to bar.ext, and create bar.ext when it doesn't exist. We can also specify paths to the file, but it is always ideal to put quotes (") around paths, see here for the reason.


There are also many flags available for copy, see copy /? or help copy on a command prompt to see more.

Editing Nth Line of a File

Batch file does not come with a built-in method for replacing nth line of a file except replace and append(> and >>). Using for loops, we can emulate this kind of function.


@echo off
set file=new2.txt

call :replaceLine "%file%" 3 "stringResult"

type "%file%"
pause
exit /b

:replaceLine <fileName> <changeLine> <stringResult>
setlocal enableDelayedExpansion

set /a lineCount=%~2-1

for /f %%G in (%~1) do (
    if !lineCount! equ 0 pause & goto :changeLine
    echo %%G>>temp.txt
    set /a lineCount-=1
)

:changeLine
echo %~3>>temp.txt

for /f "skip=%~2" %%G in (%~1) do (
    echo %%G>>temp.txt
)

type temp.txt>%~1
del /f /q temp.txt

endlocal
exit /b
  • The main script calls the function replaceLine, with the filename/ which line to change/ and the string to replace.

  • Function receives the input

    • It loops through all the lines and echo them to a temporary file before the replacement line
    • It echoes the replacement line to the file
    • It continues to output to rest of the file
    • It copies the temporary file to the original file
    • And removes the temporary file.
  • The main script gets the control back, and type the result.