49 lines
931 B
Go
49 lines
931 B
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 10.
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//!+
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// Dup2 prints the count and text of lines that appear more than once
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// in the input. It reads from stdin or from a list of named files.
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package main
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import (
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"bufio"
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"fmt"
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"os"
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)
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func main() {
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counts := make(map[string]int)
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files := os.Args[1:]
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if len(files) == 0 {
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countLines(os.Stdin, counts)
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} else {
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for _, arg := range files {
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f, err := os.Open(arg)
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if err != nil {
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fmt.Fprintf(os.Stderr, "dup2: %v\n", err)
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continue
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}
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countLines(f, counts)
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f.Close()
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}
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}
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for line, n := range counts {
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if n > 1 {
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fmt.Printf("%d\t%s\n", n, line)
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}
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}
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}
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func countLines(f *os.File, counts map[string]int) {
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input := bufio.NewScanner(f)
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for input.Scan() {
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counts[input.Text()]++
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}
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// NOTE: ignoring potential errors from input.Err()
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}
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//!-
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