How to grep number of unique occurrences

Question

I understand that grep -c string can be used to count the occurrences of a given string. What I would like to do is count the number of unique occurrences when

Answer 1

Here's an awk script:

#!/usr/bin/awk -f

BEGIN {
    file = ARGV[1]
    while ((getline line < file) > 0) {
        for (i = 2; i < ARGC; ++i) {
            p = ARGV[i]
            if (line ~ p) {
                a[p] += !a[p, line]++
            }
        }
    }
    for (i = 2; i < ARGC; ++i) {
        p = ARGV[i]
        printf("%s = %d occurrences\n", p, a[p])
    }
    exit
}

Example:

awk -f script.awk somefile ab sh

Output:

ab = 7 occurrences
sh = 2 occurrences