Значение переменной FN

Выражение

Возвращаемый результат

FN="my filename with spaces.txt"

${FN/ /_}

my_filename with spaces.txt

FN="my filename with spaces.txt"

${FN// /_}

my_filename_with_spaces.txt

FN="my filename with spaces.txt"

${FN// /}

myfilenamewithspaces.txt

FN="/usr/bin/filename"

${FN//\// }

usr bin filename

FN="/usr/bin/filename"

${FN/\// }

usr/bin/filename