"cat" Command

Learn all about cat command

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The cat (short for concatenate) command is one of the most frequently used command in Linux/Unix like operating systems. cat command allows us to create single or multiple files, view contents of file, concatenate files and redirect output in terminal or files. In this article, we are going to find out handy use of cat commands with their examples. More Information can be found on its manual page.

root:~# man cat

Example-1

1.1 In the below example, it will show contents of /etc/passwd file.

root:~# cat /etc/passwd
root:x:0:0::/root:/bin/bash
other:x:0:0:root:/.other:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/bin/sh

1.2 To view, contents of multiple files.

root:~#cat test test1
Hello World !
Hi ! There

1.3 cat command can be used to create file.

root:~#cat > test2
Hello world. How are you?

root:~#cat test2
Hello world. How are you?

Press ctrl + d once user is done writing.

Example-2

2.1 To print line number use -n

root:~# cat /etc/passwd
1 root:x:0:0::/root:/bin/bash
2 other:x:0:0:root:/.other:/bin/bash
3 daemon:x:1:1:daemon:/usr/sbin:/bin/sh

2.2 To display $ at end of file use -e option

root:~# cat -e /etc/passwd
root:x:0:0::/root:/bin/bash$
other:x:0:0:root:/.other:/bin/bash$
daemon:x:1:1:daemon:/usr/sbin:/bin/sh$

Example-3

3.1 Use Standard Output with Redirection Operator >

root:~# cat test
Hello World !

root:~# cat test1
Hi ! There

root:~# cat test > test1
root:~# cat test1
Hello World !

3.2 Appending Standard Output with Redirection Operator >>

root:~# cat test
Hello World !

root:~# cat test2
Hi ! There

root:~# cat test >> test2
root:~# cat test2
Hi ! There
Hello World !

3.3 Redirecting Standard Input with Redirection Operator <

root:~# cat < test
Hello World !

3.4 Redirecting Multiple Files output into a Single File

root:~# cat test test1 test2 > test3
root:~# cat test3
Hello World !
Hello World !
Hi ! There
Hello World !