package container import ( "bytes" "github.com/docker/docker/api/types" "github.com/docker/docker/client" "github.com/docker/docker/pkg/stdcopy" "golang.org/x/net/context" ) // ExecResult represents a result returned from Exec() type ExecResult struct { ExitCode int outBuffer *bytes.Buffer errBuffer *bytes.Buffer } // Stdout returns stdout output of a command run by Exec() func (res *ExecResult) Stdout() string { return res.outBuffer.String() } // Stderr returns stderr output of a command run by Exec() func (res *ExecResult) Stderr() string { return res.errBuffer.String() } // Combined returns combined stdout and stderr output of a command run by Exec() func (res *ExecResult) Combined() string { return res.outBuffer.String() + res.errBuffer.String() } // Exec executes a command inside a container, returning the result // containing stdout, stderr, and exit code. Note: // - this is a synchronous operation; // - cmd stdin is closed. func Exec(ctx context.Context, cli client.APIClient, id string, cmd []string) (ExecResult, error) { // prepare exec execConfig := types.ExecConfig{ AttachStdout: true, AttachStderr: true, Cmd: cmd, } cresp, err := cli.ContainerExecCreate(ctx, id, execConfig) if err != nil { return ExecResult{}, err } execID := cresp.ID // run it, with stdout/stderr attached aresp, err := cli.ContainerExecAttach(ctx, execID, types.ExecStartCheck{}) if err != nil { return ExecResult{}, err } defer aresp.Close() // read the output var outBuf, errBuf bytes.Buffer outputDone := make(chan error) go func() { // StdCopy demultiplexes the stream into two buffers _, err = stdcopy.StdCopy(&outBuf, &errBuf, aresp.Reader) outputDone <- err }() select { case err := <-outputDone: if err != nil { return ExecResult{}, err } break case <-ctx.Done(): return ExecResult{}, ctx.Err() } // get the exit code iresp, err := cli.ContainerExecInspect(ctx, execID) if err != nil { return ExecResult{}, err } return ExecResult{ExitCode: iresp.ExitCode, outBuffer: &outBuf, errBuffer: &errBuf}, nil }