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cat.go
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cat.go
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// Copyright 2012-2017 the u-root Authors. All rights reserved
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Cat concatenates files and prints to stdout.
//
// Synopsis:
// cat [-u] [FILES]...
//
// Description:
// If no files are specified, read from stdin.
//
// Options:
// -u: ignored flag
package main
import (
"flag"
"io"
"log"
"os"
)
var (
_ = flag.Bool("u", false, "ignored")
)
func catFile(w io.Writer, file string) error {
f, err := os.Open(file)
if err != nil {
return err
}
defer f.Close()
_, err = io.Copy(w, f)
return err
}
func cat(w io.Writer, files []string) error {
for _, name := range files {
if err := catFile(w, name); err != nil {
return err
}
}
return nil
}
func main() {
flag.Parse()
if flag.NArg() == 0 {
if _, err := io.Copy(os.Stdout, os.Stdin); err != nil {
log.Fatalf("error concatenating stdin to stdout: %v", err)
}
}
if err := cat(os.Stdout, flag.Args()); err != nil {
log.Fatalf("cat: %v", err)
}
}