Manual Pages  — CAT

The options are as follows:

-b
	Number the non-blank output lines, starting at 1.
-e
	Display non-printing characters (see the -v option), and display a dollar sign (‘amp;$’) at the end of each line.
-l
	Set an exclusive advisory lock on the standard output file descriptor. This lock is set using fcntl(2) with the F_SETLKW command. If the output file is already locked, cat will block until the lock is acquired.
-n
	Number the output lines, starting at 1.
-s
	Squeeze multiple adjacent empty lines, causing the output to be single spaced.
-t
	Display non-printing characters (see the -v option), and display tab characters as ‘^I’.
-u
	Disable output buffering.
-v
	Display non-printing characters so they are visible. Control characters print as ‘^X’ for control-X; the delete character (octal 0177) prints as ‘^?’. Non- ASCII characters (with the high bit set) are printed as ‘M-’ (for meta) followed by the character for the low 7 bits.

will sequentially print the contents of file1 and file2 to the file file3, truncating file3 if it already exists. See the manual page for your shell (e.g., sh(1)) for more information on redirection.

The command:

    cat file1 - file2 - file3

will print the contents of file1, print data it receives from the standard input until it receives an EOF ('^D') character, print the contents of file2, read and output contents of the standard input again, then finally output the contents of file3. Note that if the standard input referred to a file, the second dash on the command-line would have no effect, since the entire contents of the file would have already been read and printed by cat when it encountered the first '-' operand.

Rob Pike, USENIX Summer Conference Proceedings, UNIX Style, or cat -v Considered Harmful, 1983.