demo-shift.sh

#!/bin/bash
# This script can clean up files that were last accessed over 365 days ago.
USAGE="Usage: $0 dir1 dir2 dir3 ... dirN"
if [ "$#" == "0" ]; then
    echo "$USAGE"
    exit 1
fi
while (( "$#" )); do
    if [[ $(ls "$1") == "" ]]; then
        echo "Empty directory, nothing to be done."
    else
        find "$1" -type f -a -atime +365 -exec rm -i {} \;
    fi
shift
done


#A shift statement is typically used when the number of arguments to a command is not known in advance, for
#instance when users can give as many arguments as they like. In such cases, the arguments are usually
#processed in a while loop with a test condition of (( $# )). This condition is true as long as the number of
#arguments is greater than zero. The $1 variable and the shift statement process each argument. The number of
#arguments is reduced each time shift is executed and eventually becomes zero, upon which the while loop
#exits.
#The example below, cleanup.sh, uses shift statements to process each file in the list generated by find: