Append the content in file1 and cat par.3 par.4 par.5 >> report -> contents of files par.2 par.4 par.5 appended to file report

cat file1>file1 - file emptied and cat par.3 par.4 par.5 >> report -> contents of files par.2 par.4 par.5 appended to file report

Both will do the same poeration. Will append the data to the destination files.

cat file1>file1 - Wont do any operation in file 1 and cat par.3 par.4 par.5 >> report -> contents of files par.2 par.4 par.5 appended to file report