cat Command

Purpose

Concatenates or displays files.

Syntax

cat [ - q ] [ -r ] [ - s ] [ - S ] [ - u ][ - Z ] [ - 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, > (greater than symbol). 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.

Note: The I/O buffer size for the read and write system calls generated by this command can be configured by using the AIX_STDBUFSZ environment variable.

Flags

Item	Description
-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.
Z	Dumps the contents of encrypted files in encrypted format. Access keys to the encrypted file are not required to do cat -Z on the file.

Exit Status

This command returns the following exit values:

Item	Description
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. 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.
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

Item	Description
/usr/bin/cat	Contains the cat command.