cat(1)

NAME

cat — concatenate, copy, and print files

SYNOPSIS

cat [-benrstuv] file ...

DESCRIPTION

cat reads each file in sequence and writes it on the standard output. Thus:

cat file

prints file on the default standard output device;

cat file1 file2 > file3

concatenates file1 and file2, and places the result in file3.

If - is appears as a file argument, cat uses standard input. To combine standard input and other files, use a combination of - and file arguments.

Options

cat recognizes the following options:

-b: Omit line numbers from blank lines when -n option is specified. If this option is specified, the -n option is automatically selected.
-e: Print a $ character at the end of each line (prior to the new-line). If this option is specified, the -v option is automatically selected.
-n: Display output lines preceded by line numbers, numbered sequentially from 1.
-r: Replace multiple consecutive empty lines with one empty line, so that there is never more than one empty line between lines containing characters.
-s: Silent option. cat suppresses error messages about non-existent files, identical input and output, and write errors. Normally, input and output files cannot have identical names unless the file is a special file.
-t: Print each tab character as ^I and form feed character as ^L. If this option is specified, the -v option is automatically selected.
-u: Do not buffer output (handle character-by-character). Normally, output is buffered.
-v: Cause non-printing characters (with the exception of tabs, new-lines and form-feeds) to be printed visibly. Control characters are printed using the form ^X (Ctrl-X), and the DEL character (octal 0177) is printed as ^? (see ascii(5)). Single-byte control characters whose most significant bit is set, are printed using the form M-^x, where x is the character specified by the seven low order bits. All other non-printing characters are printed as M-x, where x is the character specified by the seven low order bits. This option is influenced by the LC_CTYPE environment variable and its corresponding code set.

EXTERNAL INFLUENCES

Environment Variables

LANG provides a default value for the internationalization variables that are unset or null. If LANG is unset or null, the default value of "C" (see lang(5)) is used. If any of the internationalization variables contains an invalid setting, cat will behave as if all internationalization variables are set to "C". See environ(5).

LC_ALL If set to a non-empty string value, overrides the values of all the other internationalization variables.

LC_CTYPE determines the interpretation of text as single and/or multi-byte characters, the classification of characters as printable, and the characters matched by character class expressions in regular expressions.

LC_MESSAGES determines the locale that should be used to affect the format and contents of diagnostic messages written to standard error and informative messages written to standard output.

NLSPATH determines the location of message catalogues for the processing of LC_MESSAGES.

International Code Set Support

Single- and multi-byte character code sets are supported.

RETURN VALUE

Exit values are:

0: Successful completion.
>0: Error condition occurred.

EXAMPLES

To create a zero-length file, use any of the following:

cat /dev/null > file
cp /dev/null file
touch file

The following prints ^I for all the occurrences of tab character in file1

cat -t file1

To suppress error messages about files that do not exist, use:

cat -s file1 file2 file3 > file

If file2 does not exist, the above command concatenates file1 and file3 without reporting the error on file2. The result is the same if -s option is not used, except that cat displays the error message.

To view non-printable characters in file2, use:

cat -v file2

WARNINGS

Command formats such as

cat file1 file2 > file1

overwrites the data in file1 before the concatenation begins, thus destroying the file. Therefore, be careful when using shell special characters.

STANDARDS CONFORMANCE

cat: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2