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readlink.go
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readlink.go
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// Copyright 2013-2022 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.
// readlink display value of symbolic link file.
//
// Synopsis:
//
// readlink [OPTIONS] [FILE...]
//
// Options:
//
// -f: follow
// -n: nonewline
// -v: verbose
package main
import (
"flag"
"fmt"
"io"
"os"
"path/filepath"
)
const cmd = "readlink [-fnv] FILE"
var (
follow = flag.Bool("f", false, "follow recursively")
noNewLine = flag.Bool("n", false, "do not output trailing newline")
verbose = flag.Bool("v", false, "report error messages")
)
func init() {
defUsage := flag.Usage
flag.Usage = func() {
os.Args[0] = cmd
defUsage()
}
}
func readLink(stdout io.Writer, file string) error {
path, err := os.Readlink(file)
if err != nil {
return err
}
if *follow {
path, err = filepath.EvalSymlinks(file)
}
delimiter := "\n"
if *noNewLine {
delimiter = ""
}
fmt.Fprintf(stdout, "%s%s", path, delimiter)
return err
}
func run(stdout io.Writer, stderr io.Writer, args []string) error {
if len(args) == 0 {
if *verbose {
fmt.Fprintf(stderr, "missing operand")
}
return fmt.Errorf("missing operand")
}
var runErr error
for _, file := range args {
err := readLink(stdout, file)
if err != nil {
if *verbose {
fmt.Fprintf(stderr, "%v\n", err)
}
runErr = err
}
}
return runErr
}
func main() {
flag.Parse()
if err := run(os.Stdin, os.Stderr, flag.Args()); err != nil {
os.Exit(1)
}
}