Counting Things

The wc (word count) utility counts lines, words, and characters in one or more input files. Its usage is:

wc [-lwc] [ files ... ]

If no files are specified on the command line, wc reads its standard input. If there are multiple files, it will also print total counts for all the files. The options and their meanings are:

-l

Only count lines.

-w

Only count words. A "word" is a contiguous sequence of non-whitespace characters, separated by spaces and/or tabs. Happily, this is the normal way awk separates fields in its input data.

-c

Only count characters.

Implementing wc in awk is particularly elegant, since awk does a lot of the work for us; it splits lines into words (i.e. fields) and counts them, it counts lines (i.e. records) for us, and it can easily tell us how long a line is.

This version uses the getopt library function (see section Processing Command Line Options), and the file transition functions (see section Noting Data File Boundaries).

This version has one major difference from traditional versions of wc. Our version always prints the counts in the order lines, words, and characters. Traditional versions note the order of the `-l', `-w', and `-c' options on the command line, and print the counts in that order.

The BEGIN rule does the argument processing. The variable print_total will be true if more than one file was named on the command line.

# wc.awk --- count lines, words, characters
# Arnold Robbins, arnold@gnu.ai.mit.edu, Public Domain
# May 1993

# Options:
#    -l    only count lines
#    -w    only count words
#    -c    only count characters
#
# Default is to count lines, words, characters

BEGIN {
    # let getopt print a message about
    # invalid options. we ignore them
    while ((c = getopt(ARGC, ARGV, "lwc")) != -1) {
        if (c == "l")
            do_lines = 1
        else if (c == "w")
            do_words = 1
        else if (c == "c")
            do_chars = 1
    }
    for (i = 1; i < Optind; i++)
        ARGV[i] = ""

    # if no options, do all
    if (! do_lines && ! do_words && ! do_chars)
        do_lines = do_words = do_chars = 1

    print_total = (ARGC - i > 2)
}

The beginfile function is simple; it just resets the counts of lines, words, and characters to zero, and saves the current file name in fname.

The endfile function adds the current file's numbers to the running totals of lines, words, and characters. It then prints out those numbers for the file that was just read. It relies on beginfile to reset the numbers for the following data file.

function beginfile(file)
{
    chars = lines = words = 0
    fname = FILENAME
}

function endfile(file)
{
    tchars += chars
    tlines += lines
    twords += words
    if (do_lines)
        printf "\t%d", lines
    if (do_words)
        printf "\t%d", words
    if (do_chars)
        printf "\t%d", chars
    printf "\t%s\n", fname
}

There is one rule that is executed for each line. It adds the length of the record to chars. It has to add one, since the newline character separating records (the value of RS) is not part of the record itself. lines is incremented for each line read, and words is incremented by the value of NF, the number of "words" on this line.(22)

Finally, the END rule simply prints the totals for all the files.

# do per line
{
    chars += length($0) + 1    # get newline
    lines++
    words += NF
}

END {
    if (print_total) {
        if (do_lines)
            printf "\t%d", tlines
        if (do_words)
            printf "\t%d", twords
        if (do_chars)
            printf "\t%d", tchars
        print "\ttotal"
    }
}

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