I have 225 files of text, each with 2 lines of text a header row and the numerical data. The file name that each set of text is from is what I want to add in a first column on the row with the data. I also want to remove/(not copy) the header row from all but the very first. Thus giving me only one header row at the very top.
Se eu entendi corretamente, você quer o seguinte:
for file in *.txt; do echo "$file" $(tail -n1 $file) >> output.txt; done
Em seguida, edite o arquivo output.txt para criar o cabeçalho como quiser.