What is the difference between filename=${1:-/etc/hosts} and filename=/etc/hosts?For example:filename=/etc/hostsif [ -r $filename ] && [ -s $filename ]; then    md5sum $filenameelse    echo $filename cannot be processedfiandfilename=${1:-/etc/hosts}if [ -r $filename ] && [ -s $filename ]; then    md5sum $filenameelse    echo $filename cannot be processedfi
What is the difference between filename=${1:-/etc/hosts} and filename=/etc/hosts?
bash;shell;scripting;variable