107 lines
1.7 KiB
Go
107 lines
1.7 KiB
Go
package main
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import (
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"bufio"
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"flag"
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"fmt"
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"io"
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"os"
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"path/filepath"
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"strconv"
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"git.wntrmute.dev/kyle/goutils/die"
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)
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func init() {
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flag.Usage = func() { usage(os.Stdout); os.Exit(1) }
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}
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func usage(w io.Writer) {
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progname := filepath.Base(os.Args[0])
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fmt.Fprintf(w, `Usage: %s [-nl] file start [end]
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Print a fragment of a file starting a line 'start' and ending
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at line 'end', or EOF if no end is specified.
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The -nl flag will suppress printing of line numbers.
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`, progname)
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}
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func main() {
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quiet := flag.Bool("nl", false, "No line-numbering.")
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flag.Parse()
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if flag.NArg() < 2 || flag.NArg() > 3 {
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usage(os.Stderr)
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os.Exit(1)
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}
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start, err := strconv.Atoi(flag.Arg(1))
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die.If(err)
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var end int
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var offset bool
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if flag.NArg() == 3 {
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endStr := flag.Arg(2)
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if endStr[0] == '+' {
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offset = true
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endStr = endStr[1:]
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}
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end, err = strconv.Atoi(endStr)
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die.If(err)
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if offset {
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end += start
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}
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}
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file, err := os.Open(flag.Arg(0))
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die.If(err)
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defer file.Close()
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scanner := bufio.NewScanner(file)
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// initial empty line to start numbering at 1.
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var lines = make([]string, 1)
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for scanner.Scan() {
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lines = append(lines, scanner.Text())
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}
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if end == 0 {
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end = len(lines) - 1
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}
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if end < start {
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fmt.Fprintln(os.Stderr, "[!] end < start, swapping values")
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tmp := end
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end = start
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start = tmp
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}
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var fmtStr string
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if !*quiet {
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maxLine := fmt.Sprintf("%d", len(lines))
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fmtStr = fmt.Sprintf("%%0%dd: %%s", len(maxLine))
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}
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endFunc := func(n int) bool {
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if n == 0 {
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return false
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}
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if n > end {
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return true
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}
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return false
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}
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fmtStr += "\n"
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for i := start; !endFunc(i); i++ {
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if *quiet {
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fmt.Println(lines[i])
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} else {
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fmt.Printf(fmtStr, i, lines[i])
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}
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}
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}
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