podman/utils/utils.go

package utils

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

	"github.com/containers/storage/pkg/archive"
	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
)

// ExecCmd executes a command with args and returns its output as a string along
// with an error, if any
func ExecCmd(name string, args ...string) (string, error) {
	cmd := exec.Command(name, args...)
	var stdout bytes.Buffer
	var stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	err := cmd.Run()
	if err != nil {
		return "", fmt.Errorf("`%v %v` failed: %v %v (%v)", name, strings.Join(args, " "), stderr.String(), stdout.String(), err)
	}

	return stdout.String(), nil
}

// ExecCmdWithStdStreams execute a command with the specified standard streams.
func ExecCmdWithStdStreams(stdin io.Reader, stdout, stderr io.Writer, env []string, name string, args ...string) error {
	cmd := exec.Command(name, args...)
	cmd.Stdin = stdin
	cmd.Stdout = stdout
	cmd.Stderr = stderr
	if env != nil {
		cmd.Env = env
	}

	err := cmd.Run()
	if err != nil {
		return fmt.Errorf("`%v %v` failed: %v", name, strings.Join(args, " "), err)
	}

	return nil
}

// ErrDetach is an error indicating that the user manually detached from the
// container.
var ErrDetach = errors.New("detached from container")

// CopyDetachable is similar to io.Copy but support a detach key sequence to break out.
func CopyDetachable(dst io.Writer, src io.Reader, keys []byte) (written int64, err error) {
	buf := make([]byte, 32*1024)
	for {
		nr, er := src.Read(buf)
		if nr > 0 {
			preservBuf := []byte{}
			for i, key := range keys {
				preservBuf = append(preservBuf, buf[0:nr]...)
				if nr != 1 || buf[0] != key {
					break
				}
				if i == len(keys)-1 {
					return 0, ErrDetach
				}
				nr, er = src.Read(buf)
			}
			var nw int
			var ew error
			if len(preservBuf) > 0 {
				nw, ew = dst.Write(preservBuf)
				nr = len(preservBuf)
			} else {
				nw, ew = dst.Write(buf[0:nr])
			}
			if nw > 0 {
				written += int64(nw)
			}
			if ew != nil {
				err = ew
				break
			}
			if nr != nw {
				err = io.ErrShortWrite
				break
			}
		}
		if er != nil {
			if er != io.EOF {
				err = er
			}
			break
		}
	}
	return written, err
}

// UntarToFileSystem untars an os.file of a tarball to a destination in the filesystem
func UntarToFileSystem(dest string, tarball *os.File, options *archive.TarOptions) error {
	logrus.Debugf("untarring %s", tarball.Name())
	return archive.Untar(tarball, dest, options)
}

// TarToFilesystem creates a tarball from source and writes to an os.file
// provided
func TarToFilesystem(source string, tarball *os.File) error {
	tb, err := Tar(source)
	if err != nil {
		return err
	}
	_, err = io.Copy(tarball, tb)
	if err != nil {
		return err
	}
	logrus.Debugf("wrote tarball file %s", tarball.Name())
	return nil
}

// Tar creates a tarball from source and returns a readcloser of it
func Tar(source string) (io.ReadCloser, error) {
	logrus.Debugf("creating tarball of %s", source)
	return archive.Tar(source, archive.Uncompressed)
}