Maths on Linux Terminal

 for i in {1..10}; do echo | awk -v var=$i '{print var}' ; done

[oracle@stby ~]$  for i in {1..10}; do echo | awk -v var=$i '{print var}' ; done;
1
2
3
4
5
6
7
8
9
10

----------------------------------------------------------------------
$ a=55

$ b=87

$ echo $((a+b))

[oracle@stby ~]$ a=55

[oracle@stby ~]$ b=45

[oracle@stby ~]$

[oracle@stby ~]$ echo | awk -v var0=$a -v var1=$b '{print "division is: ", var1/var0}'

division is:  0.818182

to have division :-

============

[oracle@stby ~]$ printf "%.01f\n" $(echo "scale=1; 4/9" | bc)

0.4

[oracle@stby ~]$ printf "%.02f\n" $(echo "scale=1; 4/9" | bc)

0.40

[oracle@stby ~]$ printf "%.03f\n" $(echo "scale=1; 4/9" | bc)

0.400

[oracle@stby ~]$ printf "%.03f\n" $(echo "scale=3; 4/9" | bc)

0.444

[oracle@stby ~]$ printf "%.06f\n" $(echo "scale=6; 4/9" | bc)

0.444444

[oracle@stby ~]$ # %.0nf 👉"n"--- number of digits after decimal

[oracle@stby ~]$ # scale=6 👉 numbers of decimals digits can be calculated

1. unziping 

unzip -o /path/to/source/*.zip -d /path/to/destination/

-o :- source

-d :- destination

2. cat file_name

3. strings binary_file

4. tar -cvzf backup.tar.gz --remove-files dir/

-cvzf :- create zip file

-xvzf :- extract zip file

--remove-files :- once the file archived it will then get deleted.

5. export day=Monday

unset day

6. date -d 'tomorrow'

date -d 'next week'

date -d 'next sun'

date -d 'next year'

date -d 'next month'

date -d 'next day'

date -d +'%r' for 12 hour timing

date -d +'%R' for 24 hour timing

date + %b   ---> Sep

date + %B   ---> September

date -d '+- days/months/years' +'%Y_%m_%d %H_%M_%s'   ---> like 2023_09_04 09_05_45

7. to see shell 

echo $SHELL

8. to do maths

echo $(( 5+5 ))

printf "%.0f\n" $(echo "scale=1; 2/5" | bc)   ---> 

%.0f ---> 1

%.01f --> 1.0

%.02f --> 1.00

%.03f --> 1.000

i.e %.0nf ---> n means number of digits after decimal.