Linux Admin - cut Command

cut and grep are two of the most useful and common commands for a CentOS Administrator. cut is extremely useful for dealing with delimited files such as Linux configuration files, Linux preference files, and CSV files.

Most times, cut will be used to extract specific rows out of text files. Previously, we have used cut to get a listing of all users from /etc/passwd −

[root@centosLocal centos]# cut -d":" -f1 /etc/passwd  
root 
bin 
daemon 
adm 
lp 
sync
shutdown

Above is a digested list of system users from /etc/passwd.

Some Linux utilities and applications actually save the output with the functionality of cut in mind. Following is an example of nmap output.

[root@centosLocal centos]# grep open ./http_scans.txt  
Host: 10.58.52.67 ()   Ports: 80/open/tcp//http/// 
Host: 10.58.52.132 ()  Ports: 80/open/tcp//http/// 
Host: 10.58.52.133 ()  Ports: 80/open/tcp//http/// 
Host: 10.58.52.56 ()   Ports: 80/open/tcp//http/// 
Host: 10.58.52.71 ()   Ports: 80/open/tcp//http/// 
Host: 10.58.52.132 ()  Ports: 80/open/tcp//http///

With cut, we can quickly generate a list of internal systems with port 80 listening for outside requests.

[root@centosLocal centos]# grep open ./http_scans.txt | cut -d" " -f2 >
open_http_servers.txt  
[root@centosLocal centos]# head open_http_servers.txt  
10.58.52.17 
10.58.52.29 
10.58.52.30 
10.58.52.36 
10.58.52.59 
10.58.53.89 
10.58.53.100 
10.58.54.103 
10.58.54.148 
10.58.54.152

[root@centosLocal centos]#

Cut can also be used by character count.

[root@centosLocal centos]# cut -c 1,2,3,4,5,6,7,8 lanIP-range.txt  
10.58.52 
10.58.52 
10.58.52 
10.58.52 
10.58.52 
10.58.52
10.58.53 
10.58.53 
10.58.53 
10.58.53 
10.58.53 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54 
10.58.54

[root@centosLocal centos]#

cut is a command that will be used almost daily by a CentOS Administrator. It is a life saver for parsing text and some binary files.