goutils

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main.go (763B)

      1 /*
      2 Cat concatenates and prints files.
      3 If no arguments is given, it reads from the standard input.
      4 
      5 Usage:
      6 
      7 	cat [file ...]
      8 */
      9 package main
     10 
     11 import (
     12 	"fmt"
     13 	"io"
     14 	"os"
     15 )
     16 
     17 func main() {
     18 	if len(os.Args) == 1 {
     19 		cat(os.Stdin)
     20 		return
     21 	}
     22 	for _, fname := range os.Args[1:] {
     23 		f, err := os.Open(fname)
     24 		if err != nil {
     25 			fmt.Fprintf(os.Stderr, "cat: %v\n", err)
     26 			os.Exit(1)
     27 		}
     28 		if err := cat(f); err != nil {
     29 			fmt.Fprintf(os.Stderr, "cat: %v\n", err)
     30 			f.Close()
     31 			os.Exit(1)
     32 		}
     33 		f.Close()
     34 	}
     35 }
     36 
     37 func cat(f *os.File) error {
     38 	buf := make([]byte, 8192)
     39 	for {
     40 		n, err := f.Read(buf)
     41 		if n == 0 && err == io.EOF {
     42 			break
     43 		}
     44 		if err != nil {
     45 			return err
     46 		}
     47 		_, err = os.Stdout.Write(buf[:n])
     48 		if err != nil {
     49 			return err
     50 		}
     51 	}
     52 	return nil
     53 }