batch script, renaming a xml file inside a folder - batch-file

Question

I am writing a batch file whereby I can rename a xml file name inside a folder on my Desktop.
prompt the user to key in the file name
if the file name is found, it will then prompt the user to key in an existing xml file name
if an existing xml file name, it will then prompt the user to key in a new xml file name
an overview of my contents inside a file name(bb).
this is my batch-script
#echo off
set /p fn=Enter Folder name:
if exist C:\Users\roberts\Desktop\%fn% (
set /p oldxmlname=Enter a old xml file name:
if exist C:\Users\roberts\Desktop\%fn%\%oldxmlname%.xml (
set /p newxmlname=Enter a new xml file name:
ren C:\Users\roberts\Desktop\%oldxmlname%.xml %newxmlname%.xml
echo file name changed successfully.
)
)else (
echo folder not found in path.
echo C:\Users\roberts\Desktop\%fn%
)
this is my output. The file name didn't change at all.

Answer 1

Within a block statement (a parenthesised series of statements), the entire block is parsed and then executed. Any %var% within the block will be replaced by that variable's value at the time the block is parsed - before the block is executed.
Hence, IF (something) else (somethingelse) will be executed using the values of %variables% at the time the IF is encountered. The same comment goes for the REN.
Two common ways to overcome this are 1) to use setlocal enabledelayedexpansion and use !var! in place of %var% to access the changed value of var or 2) to call a subroutine to perform further processing using the changed values.
And if an ELSE clause is used, the IF-true command must be (parenthesised), and the ) and ELSE must be on the same physical line. If ELSE-true command is (parenthesised), the ELSE and ( must be on the same physical line. There must be a Space either side of the else keyword.
A demonstration:
#echo off
SETLOCAL
cls
set var=ORIGINAL
echo Start value of var=%var%
for %%i in (1) do (SET var=AFTER
ECHO var is %var% in the for loop
)
echo Final value of var=%var%
ENDLOCAL
ECHO.
echo ---- try again with ENABLEDELAYEDEXPANSION
ECHO.
setlocal enabledelayedexpansion
set var=ORIGINAL
echo Start value of var=%var%
for %%i in (1) do (SET var=AFTER
ECHO var is %var% not !var! in the for loop
ECHO Note: in the loop VAR has old value %var% and new value !var!
)
echo Final value of var=%var%
endlocal
Note how the value of var is interpreted differently depending on the use of setlocal or setlocal enabledelayedexpansion. The !var! syntax is only available in delayedexpansion mode and accesses the value of var as it is modified in the block,

Answer 2

You left \%fn% out of the ren command, so the file you're asking to rename really doesn't exist.
You want ren C:\Users\roberts\Desktop\%fn%\%oldxmlname%.xml %newxmlname%.xml

Answer 3

Here is a method that doesn't need delayed expansion, which your code does.
When changing a variable and using it within a loop, then delayed expansion is required.
There are some quotes to protect long file/path elements and an added backslash to detect a path and not a file.
#echo off
set /p fn=Enter Folder name:
if not exist "C:\Users\roberts\Desktop\%fn%\" (
echo The engines canna take the strain captain, try again!
goto :EOF
)
set /p oldxmlname=Enter a old xml file name:
if not exist "C:\Users\roberts\Desktop\%fn%\%oldxmlname%.xml" (
echo folder not found in path.
echo "C:\Users\roberts\Desktop\%fn%"
goto :EOF
)
set /p newxmlname=Enter a new xml file name:
ren "C:\Users\roberts\Desktop\%oldxmlname%.xml" "%newxmlname%.xml"
if not errorlevel 1 (
echo file name changed successfully.
) else (
echo oops! Something is fubar
)