Принудительное освобождение разделяемой памяти

С СЭД

sed -n '
    s,^,/something/,
    1s/^/blahblahblah /
    H
    ${g;s/\n/ /gp}
' file1.txt > file2.txt

с ударом

(   printf "blahblahblah" 
    mapfile -t lines < file1.txt
    printf " /something/%s" "${lines[@]}"
    echo 
) > file2.txt

или

{   printf "blahblahblah" 
    while IFS= read -r line; do printf " /something/%s" "$line"; done < file1.txt
    echo 
} > file2.txt