Histogram with bash

Question

Currently I use:

#!/bin/bash
while read line
do
    ((histogram[${#line}]++))   
done < "${1:-/dev/stdin}"

for length in "${!histogram[@]}"; do
    printf "%-1s %s\n" "${length}" "${histogram[$length]}"
done

to generate a histogram output. But if there are no lines of length, the output automatically omit them. Is there any ways to let the function do not omit those lines? Any ideas?

Answer 1

Do you mean that you want to print a zero for every non-occurring length up to the max length? If so:

$ cat test.sh 
#!/bin/bash
while read line
do
    ((histogram[${#line}]++))
done < "${1:-/dev/stdin}"

max=0
for length in "${!histogram[@]}"
do
    if [ $length -gt $max ]
    then
        max=$length
    fi
done

for length in $(seq 0 $max)
do
    printf "%-1s %s\n" "${length}" "${histogram[$length]-0}"
done

Example run:

$ printf 'x\nfoo\n' | ./test.sh
0 0
1 1
2 0
3 1