Problem with mkgmap -c option and multiple img files

I am attempting to build a gmapsupp.img file by combining multiple .img files with mkgmap.

It works fine when the files are listed on the command line, but not when they are included in a data file with the -c option.

My command line is:

java -Xmx1000m -jar mkgmap.jar --gmapsupp -c filelist.txt

and the file is in the current directory. It is being read - confirmed by putting an invalid option in it, which generates an error message.

I have tried with the file names on separate lines, and space separated. There are about 90 files. A gmapsupp of about 4k is generated.

Any suggestions would be appreciated.

I’ve never had any success with the -c option to compile multiple files.
This is a link to an old batch file request I posted.
Triggerfish’s batch file was extremely helpful.

I use the -c to compile multiple img files as a matter of course during my weekly builds.
Can you post your filelist.txt file somewhere?

I just saw this on the Mkgmap mailinglist, maybe it helps:

Many thanks all. I have now found the answer - it is that each line in the file must be prefixed with