cmd/build_init/execution/executor.go

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package execution

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

// Executor supports chaining subcommand execution and error handling.
type Executor struct {
	stdout io.Writer
	stderr io.Writer
}

// NewExecutor returns a new Executor that writes to stdout and stderr.
func NewExecutor(stdout, stderr io.Writer) *Executor {
	return &Executor{stdout: stdout, stderr: stderr}
}

// Exec runs the command at path with args.
func (e Executor) Exec(path string, args ...string) error {
	cmd := exec.Cmd{
		Path:   path,
		Args:   append([]string{path}, args...),
		Env:    os.Environ(),
		Stdout: e.stdout,
		Stderr: e.stderr,
	}
	return cmd.Run()
}

// ExecAllWithRetries runs all given commands. Upon encountering an error after
// maxTries, execution stops and the error is returned. Returns an error if an element
// in cmds is empty.
func (e Executor) ExecAllWithRetries(cmds [][]string, maxTries int) error {
	for i, cmd := range cmds {
		if len(cmd) == 0 {
			return fmt.Errorf("forbidden empty list in cmds at position %d", i)
		}
		path, args := cmd[0], cmd[1:]
		for tries := 0; tries < maxTries; tries++ {
			if err := e.Exec(path, args...); err != nil {
				io.WriteString(e.stdout, fmt.Sprintf("failed to exec cmd: %s; %v", strings.Join(cmd, " "), err))
				if tries == maxTries-1 {
					return err
				}
				continue
			}
			break
		}
	}
	return nil
}