lines.go in Go

Count lines, words, and bytes like wc, for files or stdin.

// Count lines, words, and bytes for files or stdin, like wc.
package main

import (
    "bufio"
    "fmt"
    "os"
)

type counts struct {
    lines, words, bytes int
}

func count(r *bufio.Reader) counts {
    var c counts
    scanner := bufio.NewScanner(r)
    for scanner.Scan() {
        line := scanner.Text()
        c.lines++
        c.bytes += len(line) + 1
        inWord := false
        for _, ch := range line {
            if ch == ' ' || ch == '\t' {
                inWord = false
            } else if !inWord {
                inWord = true
                c.words++
            }
        }
    }
    return c
}

func main() {
    args := os.Args[1:]
    if len(args) == 0 {
        c := count(bufio.NewReader(os.Stdin))
        fmt.Printf("%8d %8d %8d\n", c.lines, c.words, c.bytes)
        return
    }

    var total counts
    for _, name := range args {
        f, err := os.Open(name)
        if err != nil {
            fmt.Fprintf(os.Stderr, "skip %s: %v\n", name, err)
            continue
        }
        c := count(bufio.NewReader(f))
        f.Close()
        fmt.Printf("%8d %8d %8d %s\n", c.lines, c.words, c.bytes, name)
        total.lines += c.lines
        total.words += c.words
        total.bytes += c.bytes
    }
    if len(args) > 1 {
        fmt.Printf("%8d %8d %8d total\n", total.lines, total.words, total.bytes)
    }
}

How it works

1. bufio.Scanner reads line by line.
2. A word counter tracks transitions into words.
3. Multiple files also print a total row.

Keywords and builtins used here

• continue
• else
• for
• func
• if
• int
• len
• range
• return
• struct
• type
• var

The run, in numbers

Lines

59

Characters to type

1038

Tokens

295

Three-star pace

105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 169 seconds.

Type this snippet

Step 1 of 1 in Encore, step 30 of 30 in Language basics.

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