Semicolon is used to run multiple command in single line
[root@localhost ~]# touch file1 ; mkdir Dir1
Keyword "tac" is used to read reverse.
Note : Cat /Tac
root@localhost ~]# cat -n mukesh.txt
1 Hello Ji
2 Tuse Great Ho
3 You Can
4 You Will
5 Great
[root@localhost ~]# tac mukesh.txt
Great
You Will
You Can
Tuse Great Ho
Hello Ji
Now to put sequence number with cat "-n" but with tac we need to use "nl" command
[root@localhost ~]# nl mukeshji.txt
1 this is India Web Server
2 this is US Web Server
nl stands for number of lines in a file
root@localhost ~]# tac mukesh.txt | nl
1 Great
2 You Will
3 You Can
4 Tuse Great Ho
5 Hello Ji
To find out top three and bottom 3 command
Use Head and Tail Commands
root@localhost ~]# head -n 3 /etc/passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
[root@localhost ~]# tail -n 3 /etc/passwd
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
mukesh:x:1000:1000:Mukesh:/home/mukesh:/bin/bash
Tail command is used to read logs
tail -F /var/log/message
ECHO : It is used to print file.
root@localhost ~]# echo "Alpha Beta Gamma"
Alpha Beta Gamma
To add output to existing file use ">"
[root@localhost ~]# echo "this is India Web Server" > mukesh.txt
To Append use ">>"
root@localhost ~]# echo "this is US Web Server" >> mukesh.txt
Echo can also be used to create empty file
echo > mukesh.txt
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