awklib/eg/prog/dupword.awk


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# dupword --- find duplicate words in text
# Arnold Robbins, arnold@gnu.ai.mit.edu, Public Domain
# December 1991

{
    $0 = tolower($0)
    gsub(/[^A-Za-z0-9 \t]/, "");
    if ($1 == prev)
        printf("%s:%d: duplicate %s\n",
            FILENAME, FNR, $1)
    for (i = 2; i <= NF; i++)
        if ($i == $(i-1))
            printf("%s:%d: duplicate %s\n",
                FILENAME, FNR, $i)
    prev = $NF
}