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.

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).

To display a file at the workstation, enter:
```
cat notes
```
This command displays the data in the notes file.
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.
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.
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).
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.
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.

Files

/usr/bin/cat

Contains the cat command.

Related Information

The cp command.