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blog - BASH challenges.md

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+# 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
+    
+    ```bash
+    devdir="/mnt/sqlback1/LSQLSHARE01DEV"
+    if [[ ! -d "${devdir}" ]]; then
+        echo "${devdir} not found."
+    	# Create Directory
+    	mkdir -p "${devdir}"
+    fi
+    ```
+2. Given a threshold, determine if a given directory size is over the threshold.
+    
+    Example Solution
+    
+    ```bash
+    dir="/mnt/data2/backups"
+    threshold="100000000" # 100GB
+    
+    dirsize=$(/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
+    
+    ```bash
+    # 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
+    
+    ```bash
+    i=1; while [ $i -lt 65 ]; do let i=$((i+i)); print "[$i]"; done```
+    
+    ```
+    
+    Example Output
+    
+    ```
+    [2]
+    [4]
+    [8]
+    [16]
+    [32]
+    [64]
+    [128]
+    ```
+5. Write a script that, for each number from 1 to 100, prints a comma-delimited list of numbers in descending order from the current number to 1. Each list should be shown on a separate line as seen below.
+    
+    ```
+    1
+    2,1
+    3,2,1
+    4,3,2,1
+    ...
+    100,99,...,1
+    ```
+    
+    Example Solution (from 10 to save space). (OK, I cheated shaving off the trailing comma.)
+    
+    ```bash
+    echo "1"; for x in {2..10}; do for i in {$x..2}; do echo -n $i,; done; echo -n "1"; echo ""; done
+    ```
+    
+    Best Solution:
+    
+    ```bash
+    for (( i=1;i<=10;i++ )); do eval printf -- '%d\\n' "{${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