Using AWK

//print the first column
awk -F":" ' { print $1 } ' /etc/passwd  
// print 1st column and last column
awk -F":" ' { print $1, $NF} ' /etc/passwd 
//print 1st column of 1st ten records
awk -F":" ' NR==1,NR==10 { print $1 } ' /etc/passwd
//print 1st column length of 1st ten records 
awk -F":" ' NR==1,NR==10 { print length($1) } ' /etc/passwd 
// using printf to format output
awk -F":" ' NR==1,NR==10 { printf "%-8s %3d\n" , $1,$3 } ' /etc/passwd 
// add header and footer for output
awk -F":" '
BEGIN { printf "%-8s %-3s\n" , "User", "UID" }
NR==1,NR==10 { printf "%-8s %3d\n" , $1,$3 } 
END { print "============== END ============="} ' /etc/passwd
// add output filed separator between columns
awk -F":" ' { OFS="|";print $1, $NF } ' /etc/passwd
// condition
awk -F":" ' /^root/ { print $1, $NF } ' /etc/passwd
awk -F":" ' { if($1 ~ /root/) { print $1, $NF } }' /etc/passwd

 

Linux Job Interview Questions

  1. How can you see which kernel version a system is currently running?
uname -a  // Show hostname, current version, current release

uname -v  //Show current version

uname -r  // Show current release

2.How can you check a system’s current IP address?

ifconfig
ip addr show
ip addr show eth0

3. How do you check for free disk space?

df -ah

4. How dow you manage services on a system?

service <service name> status
systemctl status <service name>

5. How would you check the size of a directory’s contents on disk?

du -sh <directory name>

6. How would you check for open ports on a Linux machine?

netstat
sudo netstat  -tulpn

7. How do you check CPU usage for a process?

ps aux |grep <process name> 
top
htop

8. Dealing with Mounts

ls /mnt
mount <device/network drive> <mount point>
/etc/fstab

9. How do you look up something you don’t know?

man <command>
<command> --h
google