Write a function that takes a directory name as an argument and writes to standard output the maximum of the lengths of all filenames in that directory. If the function’s argument is not a directory name, write an error message to standard output and exit with nonzero status.

What will be an ideal response?

$ function maxfn () {
> declare -i max thisone
> if [ ! -d "$1" -o $# = 0 ]
> then
> echo "Usage: maxfn dirname"
> return 1
> fi
>
> max=0
> for fn in $(/bin/ls $1)
> do
> thisone=${#fn}
> if [ $thisone -gt $max ]
> then
> max=$thisone
> fi
> done
> echo "Longest filename is $max characters."
> }