Uly.me

cloud engineer

Fibonacci Sequence in Python

How to calculate Fibonacci sequence in Python.

Create a file called fib.py.

nterms = int(input("How many terms? "))
n1, n2 = 0, 1
count = 0
if nterms <= 0:
    print("Please enter a positive integer")
elif nterms == 1:
    print("Fibonacci sequence:")
    print(n1)
else:
    print("Fibonacci sequence:")
    while count < nterms:
        print(n1)
        nth = n1 + n2
        # update values
        n1 = n2
        n2 = nth
        count += 1

Run it.

$ python fix.py
How many terms? 5
Fibonacci sequence:
0
1
1
2
3

Again.

$ python fib.py
How many terms? 10
Fibonacci sequence:
0
1
1
2
3
5
8
13
21
34

Bash input executes functions

How to execute functions in Bash based on argument.

There are 2 functions: build and terminate.

#!/bin/bash
build () {
 echo 'Building services'
}
terminate () {
 echo 'Terminating services'
}
if [ $1 == 'build' ]; then build
elif [ $1 == 'terminate' ]; then terminate
else echo 'Valid options are "build" or "terminate"'
fi

Execute a function based on argument.

$ bash test.sh build
Building services
 
$ bash test.sh terminate
Terminating services
 
$ bash test.sh anyother
Valid options are "build" or "terminate"

AWS display Lightsail snapshots

How to display Lightsail snapshots.

#!/bin/bash
displaysnapshots () {
  echo '--------------------------------------------------------'
  aws lightsail get-instance-snapshots --query 'instanceSnapshots[].[name]' --output text | sort
  echo '--------------------------------------------------------'
}
displaysnapshots

Result.

daily_ulyme_1637812801
daily_ulyme_1637899201
daily_ulyme_1637985601
daily_ulyme_1638072001

Adding timestamp to the output.

  aws lightsail get-instance-snapshots --query 'instanceSnapshots[].[name,createdAt]' --output text | sort

Result.

daily_ulyme_1637812801	1637812806.853
daily_ulyme_1637899201	1637899208.285
daily_ulyme_1637985601	1637985606.184
daily_ulyme_1638072001	1638072006.579

Convert Unix timestamp to iso8601. Edit your ~/.aws/config file. Add this line.

cli_timestamp_format = iso8601

Result.

daily_ulyme_1637812801	2021-11-25T04:00:06.853000+00:00
daily_ulyme_1637899201	2021-11-26T04:00:08.285000+00:00
daily_ulyme_1637985601	2021-11-27T04:00:06.184000+00:00
daily_ulyme_1638072001	2021-11-28T04:00:06.579000+00:00

Delete lines using sed

How to delete a line containing a pattern using sed.

Contents of test.txt.

$ cat test.txt
one
two
three

Delete a line matching the string “one.”

sed -i '/one/d' test.txt

Display test.txt

$ cat test.txt
two
three

Bash Read File

How to read a file line by line in Bash.

#!/bin/bash
file=test.txt
while IFS= read -r line; do
  echo $line
done < $file

Contents of test.txt.

one
two
three

Results when running test.sh.

$ bash test.sh
one
two
three

To read multiple strings line by line.

#!/bin/bash
file=test.txt
while read -r a b; do
  echo $b
done < $file

Modified contents of test.txt.

one 1
two 2
three 3

New results.

$ bash test.sh
1
2
3