Linux Cat Command Usage and Examples

This post will guide you how to use cat command in Linux system. How do I use cat command to print the content of a given file under CentOS/RHEL/Ubuntu Linux.

NAME

---

cat – concatenate files and print on the standard output

SYNOPSIS

---

cat [OPTION]... [FILE]...

DESCRIPTION

---

Concatenate FILE(s), or standard input, to standard output.

-A, –show-all
equivalent to -vET

-b, –number-nonblank
number nonempty output lines, overrides -n

-e equivalent to -vE

-E, –show-ends
display $ at end of each line

-n, –number
number all output lines

-s, –squeeze-blank
suppress repeated empty output lines

-t equivalent to -vT

-T, –show-tabs
display TAB characters as ^I

-u (ignored)

-v, –show-nonprinting
use ^ and M- notation, except for LFD and TAB

–help display this help and exit

–version
output version information and exit

With no FILE, or when FILE is -, read standard input.

Linux Cat Command Examples

---

Dispaly a File with Cat command

If you want to print contents of a given file, you can use the cat command. For example, To show contents of /etc/passwd file, type the following command:

# cat /etc/passwd

Outputs:

devops@devops-osetc:~/working$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin

View Contents from multiple files

If you want to print contetns of two or more fiels in Linux, you can use the following command:

# cat fio1.txt fio2.txt

Create a New file with Cat command

If you want to create a new file, you can also use the cat command to achieve it. Just type the following command to create a new file called fio.txt:

# cat >fio.txt

View A Large File with Cat Command

If you have a large file and you want to print the content of that file, and you can use the cat command with Less or more command, type:

# cat large.txt | less

Or

# cat large.txt | more

Display Line Numbers in File with Cat Command

If you want to print the contents of file with line numbers, and you can use cat command with -n option, type:

# cat -n /etc/passwd

Outputs:

devops@devops-osetc:~/working$ cat -n /etc/passwd
1 root:x:0:0:root:/root:/bin/bash
2 daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
3 bin:x:2:2:bin:/bin:/usr/sbin/nologin
4 sys:x:3:3:sys:/dev:/usr/sbin/nologin
5 sync:x:4:65534:sync:/bin:/bin/sync
6 games:x:5:60:games:/usr/games:/usr/sbin/nologin

Appending Data to A File with Cat command

If you want to append data into an existing file, you can use the following command:

# cat >> fio.txt

Outputs:

devops@devops-osetc:~/working$ cat >>fio.txt
sdfskdf
sdkfsdkjf
lsdfsjdf
devops@devops-osetc:~/working$
devops@devops-osetc:~/working$ cat fio.txt
sdfskdf
sdkfsdkjf
lsdfsjdf