Number of non repeating lines - unique count

Question

Here is my problem: Any number of lines of text is given from standard input. Output: number of non repeating lines

INPUT:

She is we         


        

Answer 1

Here's how I'd solve the problem:

... | awk '{n[$0]++} END {for (line in n) if (n[line]==1) num++; print num}'

But that's pretty opaque. Here's a (slightly) more legible way to look at it (requires bash version 4)

... | {
    declare -A count    # count is an associative array

    # iterate over each line of the input
    # accumulate the number of times we've seen this line
    #
    # the construct "IFS= read -r line" ensures we capture the line exactly

    while IFS= read -r line; do
        (( count["$line"]++ ))
    done

    # now add up the number of lines who's count is only 1        
    num=0
    for c in "${count[@]}"; do
        if (( $c == 1 )); then
            (( num++ ))
        fi
    done

    echo $num
}