cat Command

Purpose:

Concatenates or displays files.

Syntax:

cat [ - q ] [ -r ] [ - s ] [ - S ] [ - u ] [ - n [ - b ] ] [ - v [ - e ] [ - t
] ] [ - | File ... ]

Description:

The cat command reads each File parameter in sequence and writes it to standard
output. If you do not specify a file name, the cat command reads from standard
input. You can also specify a file name of - (dash) for standard input.
Attention: Do not redirect output to one of the input files using the
redirection symbol, > (caret). If you do this, you lose the original data in
the input file because the shell truncates the file before the cat command can
read it. See "Redirecting Input and Output in the Korn Shell" in AIX 5L Version
5.2 System User's Guide: Operating System and Devices for more information.

Flags:

-b Omits line numbers from blank lines, when specified with the -n flag.

-e Displays a $ (dollar sign) at the end of each line, when specified with the
-v flag.

-n Displays output lines preceded by line numbers, numbered sequentially from
1.

-q Does not display a message if the cat command cannot find an input file.
This flag is identical to the -s flag.

-r Replaces multiple consecutive empty lines with one empty line. This flag is
identical to the -S flag.

-s Does not display a message if the cat command cannot find an input file.
This flag is identical to the -q flag. Note: Previously, the -s flag handled
tasks now assigned to the -S flag.

-S Replaces multiple consecutive empty lines with one empty line. This flag is
identical to the -r flag.

-t Displays tab characters as ^I if specified with the -v flag.

-u Does not buffer output. The default is buffered output.

-v

Displays nonprinting characters as visible characters, with the exception of
tabs, new-lines, and form-feeds. ASCII control characters (octal 000-037) are
printed as ^n, where n is the corresponding ASCII character in the octal range
100-137 (@, A, B, C,..., X, Y, Z, [, \, ], ^, and _); the DEL character (octal
0177) is printed as ^?. Other non-printable characters are printed as M-x,
where x is the ASCII character specified by the low-order seven bits.

When used with the -v option, the following options may be used:

-e
A $ character will be printed at the end of each line prior to a new line.
-t
Tabs will be printed as ^I and form feeds will be printed as ^L

The -e and -t options are ignored if the -v option is not specified.

- Allows standard input to the cat command.

Exit Status

This command returns the following exit values:

0 All input files were output successfully.

>0 An error occurred.

Examples:

Attention: Do not redirect output to one of the input files using the
redirection symbol, > (caret).

1. To display a file at the workstation, enter:

cat notes

This command displays the data in the notes file. If the file is more than
one less than the number of available display lines, some of the file
scrolls off the screen. To list a file one page at a time, use the pg
command.
2. To concatenate several files, enter:

cat section1.1 section1.2 section1.3 >section1

This command creates a file named section1 that is a copy of section1.1
followed by section1.2 and section1.3.
3. To suppress error messages about files that do not exist, enter:

cat -q section2.1 section2.2 section2.3 >section2

If section2.1 does not exist, this command concatenates section2.2 and
section2.3. The result is the same if you do not use the -q flag, except
that the cat command displays the error message:

cat: cannot open section2.1

You may want to suppress this message with the -q flag when you use the
cat command in shell procedures.
4. To append one file to the end of another, enter:

cat section1.4 >> section1

The >> (two carets) appends a copy of section1.4 to the end of section1.
If you want to replace the file, use the > (caret).
5. To add text to the end of a file, enter:

cat >>notes

Get milk on the way home

Ctrl-D

This command adds Get milk on the way home to the end of the file called
notes. The cat command does not prompt; it waits for you to enter text.
Press the Ctrl-D key sequence to indicate you are finished.
6. To concatenate several files with text entered from the keyboard, enter:

cat section3.1 - section3.3 >section3

This command concatenates the file section3.1 with text from the keyboard
(indicated by the minus sign), and the file section3.3, then directs the
output into the file called section3.