CAT(1)

SYNOPSIS

cat [-us] [-n|-b] [-TEv] [-teA] [file]…

DESCRIPTION

Copies each file (standard input stream if "-", the default), in order, to the standard output stream. In case of an input error, the file is skipped but processing continues.

OPTIONS

-u: Don't buffer output. Input is never buffered.
-s, --squeeze-blank: Replace runs of empty input lines with a single one.
-n, --number: Number lines from 1, separating them from the file contents with a tab.
-b, --number-nonblank: Likewise, but don't number empty lines.
-T, --show-tabs: Replace tab characters with "^I".
-E, --show-ends: Prepend newlines with a dollar ("$").
-v, --show-nonprinting: Replace non-printable bytes ([0, 0x1F] ∪ [0x7F, 0xFF] - {0x09 (tab), 0x0A (newline)}) with their corresponding "^c" and "M-c" escapes (see STANDARDS, Escapes).
-t: -Tv
-e: -Ev
-A, --show-all: -TEv

EXIT STATUS

1 if a file couldn't be opened or read.

EXAMPLES

$ echo echoed | cat
echoed

$ echo abcdefg | split -b3
$ printf : | cat xaa - xab - xac
abc:defg
$ cat xaa - xab - xac  # teletype input bolded
abcA
A
^DdefB
B
^Dg

$ cat form
Groceries for February:


        Bananas 3.5kg   $4.51
        Kiwis   2kg     $3.19   Call Siegfried to explain short!
        Bread           $20.21
$ cat -sbte form
     1  Groceries for February:$
$
     2  ^IBananas^I3.5kg^I$4.51$
     3  ^IKiwis^I2kg^I$3.19^ICall Siegfried to explain short!$
     4  ^IBread^I^I$20.21$

STANDARDS

Conforms to IEEE Std 1003.1-2008 (“POSIX.1”); -u is the only flag specified by the standard. -nb, -s, -tev compatible with 4BSD. Remaining flags (-TEA) compatible with the GNU system.

Escapes

0x0

0x1

0x2

0x3

0x4

0x5

0x6

0x7

0x8

0x9

0xA

0xB

0xC

0xD

0xE

0xF

0x00

^@

^A

^B

^C

^D

^E

^F

^G

^H

^I

^K

^L

^M

^N

^O

0x10

^P

^Q

^R

^S

^T

^U

^V

^W

^X

^Y

^Z

^[

^\

^]

^^

^_

0x70

^?

Above 0x80, the table repeats but with M- prepended (i.e. 0xC1 is M-A and 0x8A — M-^J).

HISTORY

Appears in the first edition of the UNIX Programmer's Manual as cat(I):

NAME: cat -- concatenate and print
SYNOPSIS: cat file1 ...

With the standard input stream used if no files, as present-day.

Version 3 AT&T UNIX adds the "-"-as-standard-input-stream behaviour. This can safely be considered fully-formed.

Version 7 AT&T UNIX sees a rewrite in C with <stdio.h>, and -u disabling buffering of the standard output stream (considering it feeds getc() directly into putchar() until end-of-file, this is a significant penalty, but is, regardless, most likely decidedly slower than the previous implementation, which mapped full-block read(II)s onto write(II)s). It also explicitly checks for, skips, and warns about one of the input files also being bound to the standard output stream.

3BSD uses a larger, 1024-byte BUFSIZ, and hence output buffer.

4BSD introduces -nb, -s, and -tve — all as today.

4.3BSD sees a fast read(2)/write(2) path if no flags were specified.

Programmer's Workbench (PWB/UNIX), instead, sees -s, silencing errors, and a re-write in terms of read(2)/write(2). Oddly, AT&T System III UNIX inherits this -s into an Version 7 AT&T UNIX base.

AT&T System V Release 2 UNIX also sees -tve, except -te require -v to activate, -t also controls 0x12 (form feed), and M-^J (newline + high bit) is M-$<newline>. The former can be attributed to implementing according to the 4BSD manpage, which erroneously implies the -v requirement. The latter only to low QoI. Without -v, a block-wise read(2)/write(2) copy is performed.