Count the number of occurrences of each line in a file.

count

#!/bin/bash

# Count the number of occurrences of each line in a file.
#
# Example:
#
# test.txt:
# A
# A
# B
# C
# D
# D
# D
#
# $ count < test.txt
# 2 A
# 1 B
# 1 C
# 3 D
#
# Often useful to sort the results:
# $ count < test.txt | sort -n
# 1 B
# 1 C
# 2 A
# 3 D

awk '{ 
        c[$1]++ 
    } END { 
        for (i in c) { 
            print c[i], i 
        } 
    }'