CAT(1) General Commands Manual CAT(1)

cat — concatenate and print files

cat [-belnstuv] [file ...]

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:

Number the non-blank output lines, starting at 1.
Display non-printing characters (see the -v option), and display a dollar sign (‘$’) at the end of each line.
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.
Number the output lines, starting at 1.
Squeeze multiple adjacent empty lines, causing the output to be single spaced.
Display non-printing characters (see the -v option), and display tab characters as ‘^I’.
Disable output buffering.
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.

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

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.

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.

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

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

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.

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.

January 29, 2013 macOS 15.0