Cat reads each file in sequence and displays it on the standard output. Thus
displays the file on the standard output, and
cat file1 file2 >file3
concatenates the first two files and places the result on the third.
If no input file is given, or if the argument `-' is encountered, cat reads from the standard input file. Output is buffered in the block
size recommended by stat(2) unless the standard output is a terminal, when it is line buffered. The -u option makes the output completely
The -n option displays the output lines preceded by lines numbers, numbered sequentially from 1. Specifying the -b option with the -n
option omits the line numbers from blank lines.
The -s option crushes out multiple adjacent empty lines so that the output is displayed single spaced.
The -v option displays non-printing characters so that they are visible. Control characters print like ^X for control-x; the delete char-
acter (octal 0177) prints as ^?. Non-ascii characters (with the high bit set) are printed as M- (for meta) followed by the character of
the low 7 bits. A -e option may be given with the -v option, which displays a `$' character at the end of each line. Specifying the -t
option with the -v option displays tab characters as ^I.