With rename it is possible to bulk change filenames. I managed to get rid of all + with this command and replace them with underscores:
rename 's/\+/_/g' *
I could change normal letters like a to A with.
rename 's/a/A/g' *
but I could not rename the ?, not like this /\? and not like this /?.
Is there any way to adress the "?" in the filename? Most FTP programs fail to rename files with ? as well. Midnight Commander fails. The only way I found that works so far is:
mv ?myfile.txt myfile.txt
but this command is not flexible enough. I would prefer to bulk rename all ? in all files.