Batch file name string concatenation

Question

this problem has been bothering me for hours. I hope someone could help shed some light. Basically, I am trying to scan through all the files (of a specific type) in a folder (there are no subfolder inside, so no need to worry this case), get those files' name, and concatenate all into one string for example, if a folder has two files, a.xml, b.xml and c.xml, I want to get a string looks like

-a a.xml -a b.xml -a c.xml

Below is my code.

copy *.xml C:\FTP
setLocal Enabledelayedexpansion
set "directory=C:\temp"
set "attachment= "
set "a= -a "
for %%n in (%directory% *.xml) DO ( 
set "attachment=!attachment! %a% %directory%\%%n "
echo.%attachment%
)
setlocal disabledelayedexpansion
echo.%attachment%

The output is shown in this image http://imgur.com/vpUUe05 the problem I have is that first, all echoes in the for loop prints out nothing. as shown in those blank lines. the final string I want,i.e. attachment, contains an initial substring of

-a C:\temp\C:temp. 

This is actually not a file. the final string I want should be one that is without this substring, only those behind it. By the way, if there is no file inside the folder, I want the string "attachment" to just an empty string like "". Can anyone help me? Thanks a lot!

Solution

Inside your for loop you show the value of %attachment%, so that value is NOT updated in each iteration; you must use delayed expansion to do so.

The set of values in for command is: (%directory% *.xml) that is, the value C:\temp and all files with .xml extension, that I assumed is none in current directory. After that, you use this value in %a% %directory%\%%n expression, so the result is -a C:\temp\C:\temp. I think there is not a point here.

If you want not the folder value in the list, just don't insert it and use %~NXn modifier in the for replaceable parameter.

Below is the correct code:

copy *.xml C:\FTP
setLocal Enabledelayedexpansion
set "directory=C:\temp"
set "attachment= "
set "a= -a "
for %%n in ("%directory%\*.xml") DO ( 
set "attachment=!attachment! %a% %%~NXn "
echo.!attachment!
)
setlocal disabledelayedexpansion
echo.%attachment%

Comments

[Rookie]

Hi, Thank you so much! It works. Could I ask what is the difference btween echo.%attachment% and echo.!attachment!, and also what is %%~NXn ? Batch file seems to have so many abbreviations like, I am really blurred. Where can I find a list of these abbreviations? Thank you.