Count line lengths in file using command line tools

This

• counts the line lengths using awk, then
• sorts the (numeric) line lengths using sort -n and finally
• counts the unique line length values uniq -c.

$ awk '{print length}' input.txt | sort -n | uniq -c
      1 1
      2 2
      3 4
      1 5
      2 6
      2 7

In the output, the first column is the number of lines with the given length, and the second column is the line length.

$ perl -lne '$c{length($_)}++ }{ print qq($_ $c{$_}) for (keys %c);' file.txt

Output

6 2
1 1
4 3
7 2
2 2
5 1

Pure awk

awk '{++a[length()]} END{for (i in a) print i, a[i]}' file.txt

4 3
5 1
6 2
7 2
1 1
2 2

Using bash arrays:

#!/bin/bash

while read line; do
    ((histogram[${#line}]++))
done < file.txt

echo "Length Occurrence"
for length in "${!histogram[@]}"; do
    printf "%-6s %s\n" "${length}" "${histogram[$length]}"
done

Example run:

$ ./t.sh
Length Occurrence
1      1
2      2
4      3
5      1
6      2
7      2