MarkdownNotes/blog - BASH challenges.md

BASH Challenges

These are examples of scripting challenges I was given and helped create for interviewees

1. Check for the presence of a directory and create it if it doesn't exist

   Example Solution

   devdir="/mnt/sqlback1/LSQLSHARE01DEV"
   if [[ ! -d "${devdir}" ]]; then
       echo "${devdir} not found."
   	# Create Directory
   	mkdir -p "${devdir}"
   fi
   

2. Given a threshold, determine if a given directory size is over the threshold.

   Example Solution

   dir="/mnt/data2/backups"
   threshold="100000000" # 100GB
   
   dirsize=$(/usr/bin/du -s ${dir} | awk '{print $1}')
   
   if [[ $dirsize -gt $threshold ]]; then
       echo "Threshold Exceeded"
       /usr/bin/du -hs "${dir}"
   fi
   

3. Create and loop over an associative array. Ex. create an array of services and ports then print them

   Example Solution

   # Declare service names and ports in an array
   declare -A services=( [apache_http]=80 [apache_https]=443 [ssh]=22 [telnet]=23 )
   
   # Iterate over services and ports
   for p in "${!services[@]}"; do
       echo -e "Service: ${p} \t Port ${services[$p]}"
   done
   

   Example Output:

   Service: apache_https        Port 443
   Service: telnet              Port 23
   Service: ssh         Port 22
   Service: apache_http         Port 80
   

4. Write a short script that displays the numbers 2 through 128 in brackets (even numbers only, as seen below).

   [2]
   [4]
   [8]
   [16]
   [32]
   [64]
   [128]
   

   Example Solution

   i=1; while [ $i -lt 65 ]; do let i=$((i+i)); print "[$i]"; done```
   
   

   Example Output

   [2]
   [4]
   [8]
   [16]
   [32]
   [64]
   [128]
   

5. Write a script that, for each number from 1 to 100, prints a comma-delimited list of numbers in descending order from the current number to 1. Each list should be shown on a separate line as seen below.

   1
   2,1
   3,2,1
   4,3,2,1
   ...
   100,99,...,1
   

   Example Solution (from 10 to save space). (OK, I cheated shaving off the trailing comma.)

   echo "1"; for x in {2..10}; do for i in {$x..2}; do echo -n $i,; done; echo -n "1"; echo ""; done
   

   Best Solution:

   for (( i=1;i<=10;i++ )); do eval printf -- '%d\\n' "{${i}..1}" | paste -sd ',' -;done
   

   Example Output

   1
   2,1
   3,2,1
   4,3,2,1
   5,4,3,2,1
   6,5,4,3,2,1
   7,6,5,4,3,2,1
   8,7,6,5,4,3,2,1
   9,8,7,6,5,4,3,2,1
   10,9,8,7,6,5,4,3,2,1
   

Tags: howto