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// Copyright 2011 The Go 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 ssh
// Session implements an interactive session described in
// "RFC 4254, section 6".
import (
"encoding/binary"
"io"
"os"
)
// A Session represents a connection to a remote command or shell.
type Session struct {
// Writes to Stdin are made available to the remote command's standard input.
// Closing Stdin causes the command to observe an EOF on its standard input.
Stdin io.WriteCloser
// Reads from Stdout and Stderr consume from the remote command's standard
// output and error streams, respectively.
// There is a fixed amount of buffering that is shared for the two streams.
// Failing to read from either may eventually cause the command to block.
// Closing Stdout unblocks such writes and causes them to return errors.
Stdout io.ReadCloser
Stderr io.Reader
*clientChan // the channel backing this session
started bool // started is set to true once a Shell or Exec is invoked.
}
// Setenv sets an environment variable that will be applied to any
// command executed by Shell or Exec.
func (s *Session) Setenv(name, value string) os.Error {
n, v := []byte(name), []byte(value)
nlen, vlen := stringLength(n), stringLength(v)
payload := make([]byte, nlen+vlen)
marshalString(payload[:nlen], n)
marshalString(payload[nlen:], v)
return s.sendChanReq(channelRequestMsg{
PeersId: s.id,
Request: "env",
WantReply: true,
RequestSpecificData: payload,
})
}
// An empty mode list (a string of 1 character, opcode 0), see RFC 4254 Section 8.
var emptyModeList = []byte{0, 0, 0, 1, 0}
// RequestPty requests the association of a pty with the session on the remote host.
func (s *Session) RequestPty(term string, h, w int) os.Error {
buf := make([]byte, 4+len(term)+16+len(emptyModeList))
b := marshalString(buf, []byte(term))
binary.BigEndian.PutUint32(b, uint32(h))
binary.BigEndian.PutUint32(b[4:], uint32(w))
binary.BigEndian.PutUint32(b[8:], uint32(h*8))
binary.BigEndian.PutUint32(b[12:], uint32(w*8))
copy(b[16:], emptyModeList)
return s.sendChanReq(channelRequestMsg{
PeersId: s.id,
Request: "pty-req",
WantReply: true,
RequestSpecificData: buf,
})
}
// Exec runs cmd on the remote host. Typically, the remote
// server passes cmd to the shell for interpretation.
// A Session only accepts one call to Exec or Shell.
func (s *Session) Exec(cmd string) os.Error {
if s.started {
return os.NewError("session already started")
}
cmdLen := stringLength([]byte(cmd))
payload := make([]byte, cmdLen)
marshalString(payload, []byte(cmd))
s.started = true
return s.sendChanReq(channelRequestMsg{
PeersId: s.id,
Request: "exec",
WantReply: true,
RequestSpecificData: payload,
})
}
// Shell starts a login shell on the remote host. A Session only
// accepts one call to Exec or Shell.
func (s *Session) Shell() os.Error {
if s.started {
return os.NewError("session already started")
}
s.started = true
return s.sendChanReq(channelRequestMsg{
PeersId: s.id,
Request: "shell",
WantReply: true,
})
}
// NewSession returns a new interactive session on the remote host.
func (c *ClientConn) NewSession() (*Session, os.Error) {
ch, err := c.openChan("session")
if err != nil {
return nil, err
}
return &Session{
Stdin: &chanWriter{
packetWriter: ch,
id: ch.id,
win: ch.win,
},
Stdout: &chanReader{
packetWriter: ch,
id: ch.id,
data: ch.data,
},
Stderr: &chanReader{
packetWriter: ch,
id: ch.id,
data: ch.dataExt,
},
clientChan: ch,
}, nil
}
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