cat

CAT(1)                       General Commands Manual                      CAT(1)

NAME
     cat – concatenate and print files

SYNOPSIS
     cat [-belnstuv] [file ...]

DESCRIPTION
     The cat utility reads files sequentially, writing them to the standard
     output.  The file operands are processed in command-line order.  If file is
     a single dash (‘-’) or absent, cat reads from the standard input.  If file
     is a UNIX domain socket, cat connects to it and then reads it until EOF.
     This complements the UNIX domain binding capability available in inetd(8).

     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 (‘$’) 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.

EXIT STATUS
     The cat utility exits 0 on success, and >0 if an error occurs.

EXAMPLES
     The command:

           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.

SEE ALSO
     head(1), more(1), pr(1), sh(1), tail(1), vis(1), zcat(1), fcntl(2),
     setbuf(3)

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

STANDARDS
     The cat utility is compliant with the IEEE Std 1003.2-1992 (“POSIX.2”)
     specification.

     The flags [-belnstv] are extensions to the specification.

HISTORY
     A cat utility appeared in Version 1 AT&T UNIX.  Dennis Ritchie designed and
     wrote the first man page.  It appears to have been for cat.

BUGS
     Because of the shell language mechanism used to perform output redirection,
     the command “cat file1 file2 > file1” will cause the original data in file1
     to be destroyed!

     The cat utility does not recognize multibyte characters when the -t or -v
     option is in effect.

macOS 12.1                      January 29, 2013                      macOS 12.1