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command.go
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command.go
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package remote
import (
"fmt"
"io"
"sync"
)
// Cmd represents a remote command being prepared or run.
type Cmd struct {
// Command is the command to run remotely. This is executed as if
// it were a shell command, so you are expected to do any shell escaping
// necessary.
Command string
// Stdin specifies the process's standard input. If Stdin is
// nil, the process reads from an empty bytes.Buffer.
Stdin io.Reader
// Stdout and Stderr represent the process's standard output and
// error.
//
// If either is nil, it will be set to ioutil.Discard.
Stdout io.Writer
Stderr io.Writer
// Once Wait returns, his will contain the exit code of the process.
exitStatus int
// Internal fields
exitCh chan struct{}
// err is used to store any error reported by the Communicator during
// execution.
err error
// This thing is a mutex, lock when making modifications concurrently
sync.Mutex
}
// Init must be called by the Communicator before executing the command.
func (c *Cmd) Init() {
c.Lock()
defer c.Unlock()
c.exitCh = make(chan struct{})
}
// SetExitStatus stores the exit status of the remote command as well as any
// communicator related error. SetExitStatus then unblocks any pending calls
// to Wait.
// This should only be called by communicators executing the remote.Cmd.
func (c *Cmd) SetExitStatus(status int, err error) {
c.Lock()
defer c.Unlock()
c.exitStatus = status
c.err = err
close(c.exitCh)
}
// Wait waits for the remote command to complete.
// Wait may return an error from the communicator, or an ExitError if the
// process exits with a non-zero exit status.
func (c *Cmd) Wait() error {
<-c.exitCh
c.Lock()
defer c.Unlock()
if c.err != nil || c.exitStatus != 0 {
return &ExitError{
Command: c.Command,
ExitStatus: c.exitStatus,
Err: c.err,
}
}
return nil
}
// ExitError is returned by Wait to indicate and error executing the remote
// command, or a non-zero exit status.
type ExitError struct {
Command string
ExitStatus int
Err error
}
func (e *ExitError) Error() string {
if e.Err != nil {
return fmt.Sprintf("error executing %q: %v", e.Command, e.Err)
}
return fmt.Sprintf("%q exit status: %d", e.Command, e.ExitStatus)
}