utils.go

package main

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strings"
)

// exists returns whether the given file or directory exists or not
func exists(path string) (bool, error) {
	_, err := os.Stat(path)
	if err == nil {
		return true, nil
	}
	if os.IsNotExist(err) {
		return false, nil
	}
	return false, err
}

// copyFile copies the contents of the file named src to the file named
// by dst. The file will be created if it does not already exist. If the
// destination file exists, all it's contents will be replaced by the contents
// of the source file.
func copyFile(src, dst string) (err error) {
	in, err := os.Open(src)
	if err != nil {
		return
	}
	defer in.Close()
	out, err := os.Create(dst)
	if err != nil {
		return
	}
	defer func() {
		cerr := out.Close()
		if err == nil {
			err = cerr
		}
	}()
	if _, err = io.Copy(out, in); err != nil {
		return
	}
	err = out.Sync()
	return
}

// runCommandInPath runs a command and waits for it to exit.
// The working directory is also set.
// The stderr error message is returned on error.
func runCommandInPath(dir, name string, args ...string) error {
	// Create the command.
	var stderr bytes.Buffer
	cmd := exec.Command(name, args...)
	cmd.Stderr = &stderr
	cmd.Dir = dir

	// Start the command and wait for it to exit.
	err := cmd.Run()
	if err != nil {
		return fmt.Errorf(strings.TrimSpace(stderr.String()))
	}

	return nil
}