| CAT(1) | General Commands Manual | CAT(1) | 
cat —
| cat | [ -beflnstuv] [-Bbsize] [-]
      [file ...] | 
cat utility reads files sequentially, writing them
  to the standard output. The file operands are processed
  in command line order. A single dash represents the standard input, and may
  appear multiple times in the file list. If no
  file operands are given, standard input is read.
The word “concatenate” is just a verbose synonym for “catenate”.
The options are as follows:
-B
    bsize-b-n option, but doesn't number blank
      lines.-e-v option, and displays a dollar sign
      (‘$’) at the end of each line as
      well.-f-lF_SETLKW command. If the output file is already
      locked, cat will block until the lock is
    acquired.-n-s-t-v option, and displays tab characters
      as ‘^I’ as well.-u-u option guarantees that the output is
      unbuffered.-v^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.cat utility exits 0 on success,
  and >0 if an error occurs.
cat file1
will print the contents of file1 to the standard output.
The command:
cat file1 file2 > file3
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, UNIX Style, or cat -v Considered Harmful, USENIX Summer Conference Proceedings, 1983.
cat utility is expected to conform to the
  IEEE Std 1003.2-1992 (“POSIX.2”)
  specification.
The flags [-Bbeflnstv] are extensions to
    the specification.
cat utility appeared in
  Version 1 AT&T UNIX. Dennis Ritchie
  designed and wrote the first man page. It appears to have been
  cat(1).
cat file1 file2 > file1”
  will cause the original data in file1 to be destroyed! This is performed by
  the shell before cat is run.
| June 15, 2014 | NetBSD 10.1 |