script 1
#!/bin/bash

currentdi=$(pwd)

for item in "$currentdi"/**/*.txt; do
    if [[ -f "$item" ]]; then
        sed -i 's/oldworld/newworld/g' "$item"
    fi
done



========================================================================================
script 2

#!/bin/bash


new_folder="$HOME/new_folder"
mkdir -p "$new_folder"

for l in {a..z}; do
    for n in {1..10}; do
        filename="file${n}_${l}"
        touch "$new_folder/$filename"
    done
done

for file in "$new_folder"/*_x; do
    echo "Hello Linux" > "$file"
done

for l in {a..z}; do
    folder="$new_folder/$l"
    mkdir -p "$folder"
    mv "$new_folder"/*_$l "$folder"
done

find "$new_folder" -type f \( -name "*3*" -o -name "*4*" \) -delete

========================================================================================
script 3

#!/bin/bash
# alive2.sh

stIp=$(echo "$1" | cut -d- -f1)
endIp=$(echo "$1" | cut -d- -f2)

network_prefix=$(echo "$stIp" | cut -d. -f1-3)

stRange=$(echo "$stIp" | cut -d. -f4)
endRange=$(echo "$endIp" | cut -d. -f4)

if (( endRange >= stRange )); then
    for ((n=stRange; n<=endRange; n++)); do
        host="$network_prefix.$n"
        ping -c2 "$host" &> /dev/null
        if [ $? = 0 ]; then
            echo "$host is UP"
        else
            echo "$host is DOWN"
        fi
    done
else
    echo "The end range is smaller than the start range."
fi
