词法分析器正确输出但指针“filename”包含错误的名称

The purpose of this code is to read the following txts(d.txt,e.txt,f.txt) and do the actions that are required in order to put the alphabet with the correct order into the output.txt. The code suppose to work since in output.txt i get the correct results but there is a problem with the testing i did using the printf (it's at the end of newfile function). In order to run i give as input d.txt and output.txt. It should print The purpose of this code is to read the followi