# uniq.awk --- do uniq in awk## Requires getopt and join library functions## Arnold Robbins, arnold@skeeve.com, Public Domain# May 1993function usage(    e){    e = "Usage: uniq [-udc [-n]] [+n] [ in [ out ]]"    print e > "/dev/stderr"    exit 1}# -c    count lines. overrides -d and -u# -d    only repeated lines# -u    only non-repeated lines# -n    skip n fields# +n    skip n characters, skip fields firstBEGIN   \{    count = 1    outputfile = "/dev/stdout"    opts = "udc0:1:2:3:4:5:6:7:8:9:"    while ((c = getopt(ARGC, ARGV, opts)) != -1) {        if (c == "u")            non_repeated_only++        else if (c == "d")            repeated_only++        else if (c == "c")            do_count++        else if (index("0123456789", c) != 0) {            # getopt requires args to options            # this messes us up for things like -5            if (Optarg ~ /^[0-9]+$/)                fcount = (c Optarg) + 0            else {                fcount = c + 0                Optind--            }        } else            usage()    }    if (ARGV[Optind] ~ /^\+[0-9]+$/) {        charcount = substr(ARGV[Optind], 2) + 0        Optind++    }    for (i = 1; i < Optind; i++)        ARGV[i] = ""    if (repeated_only == 0 && non_repeated_only == 0)        repeated_only = non_repeated_only = 1    if (ARGC - Optind == 2) {        outputfile = ARGV[ARGC - 1]        ARGV[ARGC - 1] = ""    }}function are_equal(    n, m, clast, cline, alast, aline){    if (fcount == 0 && charcount == 0)        return (last == $0)    if (fcount > 0) {        n = split(last, alast)        m = split($0, aline)        clast = join(alast, fcount+1, n)        cline = join(aline, fcount+1, m)    } else {        clast = last        cline = $0    }    if (charcount) {        clast = substr(clast, charcount + 1)        cline = substr(cline, charcount + 1)    }    return (clast == cline)}NR == 1 {    last = $0    next}{    equal = are_equal()    if (do_count) {    # overrides -d and -u        if (equal)            count++        else {            printf("%4d %s\n", count, last) > outputfile            last = $0            count = 1    # reset        }        next    }    if (equal)        count++    else {        if ((repeated_only && count > 1) ||            (non_repeated_only && count == 1))                print last > outputfile        last = $0        count = 1    }}END {    if (do_count)        printf("%4d %s\n", count, last) > outputfile    else if ((repeated_only && count > 1) ||            (non_repeated_only && count == 1))        print last > outputfile}