NAME

cat − Concatenates or displays files

SYNOPSIS

cat [-benrstuv] file ...  | -

The cat command reads each specified file in sequence and writes it to standard output. 

FLAGS

-bOmits line numbers from blank lines when -n is specified. If you specify the -b flag, the -n flag is automatically invoked with it. 

-eSame as the -v flag with a $ (dollar sign) character displayed at the end of each line. 

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

-rReplaces multiple consecutive empty lines with one empty line, so that there is never more than one empty line between lines containing characters. 

-sDoes not display a message if cat cannot find an input file. (Silent option.) 

-tSame as the -v flag, with the tab character printed as <Ctrl-i> (^I). 

-uDoes not buffer output. Writes bytes from the input file to standard output without delay as each is read. 

-vDisplays nonprinting characters so that they are visible. 

DESCRIPTION

The cat command is frequently used with > (redirection symbol) to concatenate the specified files and write them to the specified destination.  (See CAUTIONS.) The cat command is also used with >> to append a file to another file. 

If you do not specify a file or if you specify - (dash) instead of file, cat reads from standard input. The cat command accepts multiple occurrences of - (dash) as a file argument. 

EXAMPLES

     1.To display the file notes, enter:

cat notes

If the file is longer than one screenful, it scrolls by too quickly to read.  To display a file one page at a time, use the more command. 

     2.To concatenate several files, enter:

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

This 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 -s section2.1 section2.2 section2.3 > section2

If section2.1 does not exist, this command concatenates section2.2 and section2.3.  Note that the message goes to standard error, so it does not appear in the output file.  The result is the same if you do not use the -s flag, except that cat displays the error message:

cat: cannot open section2.1

You may want to suppress this message with the -s 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 >> in this command specifies that a copy of section1.4 be added to the end of section1.  If you want to replace the file, use a single > symbol. 

     5.To add text to the end of a file, enter:

cat >> notes
Get milk on the way home
<Ctrl-d>

Get milk on the way home is added to the end of notes.  With this syntax, the cat command does not display a prompt; it waits for you to enter text.  Press the End-of-File key sequence (<Ctrl-d> above) to indicate you are finished. 

     6.To concatenate several files with text entered from the keyboard, enter:

cat section3.1 - section3.3 > section3

This concatenates section3.1, text from the keyboard, and section3.3 to create the file section3. 

     7.To concatenate several files with output from another command, enter:

ls  |  cat section4.1 - > section4

This copies section4.1, and then the output of the ls command to the file section4. 

     8.To get two pieces of input from the terminal (when standard input is a terminal) with a single command invocation, enter:

cat start - middle - end > file1

If standard input is a regular file, however, the preceding command is equivalent to the following:

cat start - middle /dev/null end > file1

This is because the entire contents of the file would be consumed by cat the first time it saw - (dash) as a file argument. An End-of-File condition would then be detected immediately when - (dash) appeared the second time. 

CAUTIONS

Do not redirect output to one of the input files using the > (redirection symbol).  If you do this, you lose the original data in the input file because the shell truncates it before cat can read it.  (See also the sh command.) 

RELATED INFORMATION

Commands:  more(1), pack(1)/pcat(1)/unpack(1), pg(1), pr(1), sh(1).