China DOS Union

Oh. Just took a look at the generated bpx file. Found the reason for the problem.

Hehe. Sorry about that..

This code was only tested with echo...
Didn't notice the syntax issue with ren..

@echo off & SETLOCAL EnableDelayedExpansion
dir /b /s *.txt>1.pxp
set FileEx=
for /f "tokens=* " %%i in (1.pxp) do (
set FileEx=%%i
set FileEx=!FileEx:~0,-4!
ren "!FileEx!.txt" "*.pxp"
)
pause

Now it's good.

In batch scripting (commonly used in DOS environments), the `!` here is used for enabling delayed expansion. When delayed expansion is enabled, `!variable!` is used to access the current value of a variable. The `~0,-4` part is a substring extraction operation. In batch variable substring extraction, `%variable:~start,length%` is the basic syntax. Here, `~0,-4` means to take a substring starting from index 0 and taking all characters except the last 4 characters. So it's extracting a substring starting at position 0 and excluding the last 4 characters of the `FileEx` variable.

@echo off
for /r %%a in (*.txt) do ren %%~nxa %%~na.c
pause

Originally posted by xswdong at 2007-3-31 11:06 AM:
set FileEx=!FileEx:~0,-4!
What does the ! mean here, and is -4 the 4th character from the left starting from 0? Please give an explanation.

Variable expansion with delayed expansion is enabled, so %FileEx must be written as !FileEx. ~0 means an offset of 0, extracting all characters of variable FileEx from the first one, excluding the last four.

Originally posted by bjsh at 2007-3-30 08:18 AM:
Why does flyinspace have a reversed schedule, staying up late and getting up late?

No way.

When busy, I'm really busy. Only at this time do I have time to take a look..

If I can help, I'll just write it down.

My requirement is met. Considering generality, conversely, convert.C to.TXT.

Then it needs to be changed to the following:

@echo off & SETLOCAL EnableDelayedExpansion
dir /b /s *.c>temp.pxp
set FileEx=
for /f "tokens=* " %%i in (temp.pxp) do (
set FileEx=%%i
set FileEx=!FileEx:~0,-2!
ren "!FileEx!.c" "*.txt"
)
del temp.pxp
pause


But from the perspective of simplicity, I prefer the idea of wudixin96.
When it is necessary to convert conversely, only need to reverse the extension parameters.

[ Last edited by zzhh612 on 2007-4-1 at 12:29 AM ]

I'll simplify the code

1. @echo off
   
2. for /f "tokens=1 delims=." %%i in ('dir /b /s *.txt') do ren "%%i.txt" "*.c"
   
3. pause
   

BJSH posted on: 2007-03-31 11:08

[ Last edited by bjsh on 2007-3-31 at 11:18 AM ]

@echo off
for /r %%a in (*.txt) do ren %%~nxa %%~na.c
pause

The reason why this code cannot find files in subdirectories is as follows:
%%a is the file name including the full path.
%%~nxa can only represent a file name + extension. When executing ren, it will prompt that the path to the file is not found.
ren %%~nxa %%~na.c
is equivalent to executing: ren *.txt *.c, which is only for the current directory.

So the second sentence should be: for /r path %%a in (*.txt) do ren %%a %%~na.c
which is equivalent to executing: ren path\*.txt *.c