Tips: Using the cat command in Linux.
 With no FILE, or when FILE is -, read standard input.
 Command line options I have found useful:
- n (GNU only: –number), number all output lines
 To concatenate 2 text files and write them to a new file, you can use the following command:
$ cat file1.txt file2.txt > newcombinedfile.txt
With option -n, cat can also number lines as follows:
$ cat -n file1.txt file2.txt > newnumberedfile.txt
 To concatenate 2 files, while removing header from 2nd file this following cat command came to my rescue :
$ cat userCorpus_CMU_Featurized.csv <(tail -n +2 userCorpus_OKC_Featurized.csv) > output2.csv
- Pro tip : For some weird reason, it would complain if there was a space between the < and (. Not sure why.