Chaining two or more commands together gives real power to shell. Hundreds of commands are available but combining them and using in different way is a real game. Lets get a flavor of combination of commands , some automotive and interesting commands. Do you mind taking a ☕ CUP of coffee or tea before you start?
This will tutorial will be based on scenarios. Definitely its going to be interesting one !!
Table of Content
- Working with Files
- Working with System Information
- Working with Process
Working with Files
- How to remove blank lines while you print the output?
cat -sn /proc/cpuinfo # Here s means suppress the blank lines and n is number of lines in output
- How to print the output of several files together?
cat -s file1.txt file2.txt # Here s means suppress the blank lines
- How to check files and directories size on the disk?
du -ahc /etc/ansible # Here a is used to list al files & directories, "h" is human readable and "c" is total size of files.
- How to exclude files and directories while checking size on the disk?
du --exclude="*.xml" --exclude="*.xsl" # Here we are excluding every xml and xls from the list
- How to redirect the output to new file ?
# Creating new PATH and and storing it in new file i.e. file.txt echo 'export PATH=$PATH:/usr/local/bin' >> file.txt
- How to find files that are greater than 100K and owned by particular user ?
# Finding all the txt files that have size greater than 100k and owned by user ubuntu find /home -name "*.txt" -size 100k -user ubuntu
- How to find files with specific permissions ?
# Finding files in /etc/ansible where user,others have read, group has write permissions find /etc/ansible -perm u=r,g=w,o=r # u stands for users, g for group of and o for others
- How to search a string in a directory and sub directories?
grep -r "searchme" /etc/* # Here we will find searchme in all files and folders under /etc
- How to ignore specific lines with a condition in a file?
grep -v "searchme" file.txt # Here v flag will ignore all those line which contains searchme
- How to Create a soft link?
Softlinks are are also known as symlink and dumbpointers. It is just a redirect to a real file.
ln -s myfile mylink # Here we already have myfile created and we are creating mylink
- How to sort the files according to size ?
ls --sort size -r *.org # Here we already have myfile created and we are creating mylink
- How to sort the files according to the given column values ?
ls -la | sort -n -k7 # Here ls -la list the files , n is used to sort numerical values and k denotes which column to sort ( 7th Row ) in below example
Working with System Information
- How to check devices and storage blocks in your system ?
lshw # This command has very big output , try to use grep along with it
- How to list the status of all modules in kernels?
NOTE: Kernel works as a interface between HARDWARE and SOFTWARE . It controls all the processes
lsmod # This is equivalent to /proc/modules
- How to see the High Level information of the System ?
Working with Process
- How to check all the running process with sort command ?
ps aux # Here a is for all users, x denotes all process attached to terminal and u is user oriented.
ps aux --sort=-%cpu | grep -v `whoami`
ps -eo pid,ppid,user,cmd --sort=-%mem # Here e is for every active process , o denotes user defined output and we are sorting the memory
ps -ef --sort=-%mem # Here e is for every active process , f denotes full listing
- How to work with
Bring the suspended Job in foreground, lets see an example
sleep 100 & # Run Job in background jobs # To check Jobs fg %1 # Bring background Job in foreground
- How to work with
Bring the suspended Job in Background, lets see an example
sleep 100 then clt+z # To Suspend the Job jobs # To check Jobs bg %1 # Bring stopped Job in background
- What is top command ?
top command is used to monitor and control process. There are
- How to Display free memory and used memory of the system?
vmstat 5 10 # Here 5 denotes every 5 seconds and 10 denotes for 10 iterations
In this tutorial you learnt various scenario based ubuntu commands that are useful for every administrator. You learnt how to view process , system information and saw scenario based commands. So, What commands are you going to use in your next assignment ?