Update, this seems to work: function backup { local SOURCE=$1 local DESTINATION=$2 local ID_RSA=$3 local VALID_SSH="yes"

Update, this seems to work: function backup { local SOURCE=$1 local DESTINATION=$2 local ID_RSA=$3 local VALID_SSH="yes" local RSYNC_OPTIONS=(-av --no-perms --links) if [[ "${VALID_SSH}" == "yes" ]]; then RSYNC_OPTIONS+=(-e "ssh -i ${ID_RSA}") fi rsync "${RSYNC_OPTIONS[@]}" "${SOURCE}" "${DESTINATION}" } I got lucky and found this information with an explanation at: https://www.mail-archive.com/search?l=bug-bash@gnu.org&q=subject:%22help+with+rsync+and+Missing+trailing%5C-%5C%22+in+remote%5C-shell+command.%22&o=newest&f=1 https://www.mail-archive.com/search?l=bug-bash@gnu.org&q=sub... So, is it a good advice to always use bash arrays to construct arbitrary options for commands?