What is the difference between the 'shell' channel and the 'exec' channel in JSch

Question

I want to be able to send many consecutive command represented as strings within a Java application to a SSH server for execution. Should I use:

Channel cha         


        

Answer 1

well, I found out that this works and it's really convenient if you want to preserve state like a regular shell would:

Session session = jsch.getSession(user, host, 22);

Channel channel = session.openChannel("shell");

OutputStream inputstream_for_the_channel = channel.getOutputStream();
PrintStream commander = new PrintStream(inputstream_for_the_channel, true);

channel.setOutputStream(System.out, true);

channel.connect();

commander.println("ls -la");    
commander.println("cd folder");
commander.println("ls -la");
commander.println("exit");
commander.close();

do {
    Thread.sleep(1000);
} while(!channel.isEOF());

session.disconnect();

You could change

channel.setOutputStream(System.out, true);

with

InputStream outputstream_from_the_channel = channel.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(outputstream_from_the_channel));
String line;
while ((line = br.readLine()) != null)
    System.out.print(line+"\n");

if you want more control on the output.

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EDITED: follow up

why sometimes the commands I send through the PrintStream appear randomly in the output. i.e. the following code:

shell[0].println("cd ..");
shell[0].println("cd ..");
shell[0].println("ls -la");
shell[0].println("exit");

produces this: (marked with {thing} are things that shouldnt be there!)

Last login: Thu Jul 21 21:49:13 2011 from gateway

Manifests: trunk-latest

[host ~]$ cd ..
{cd ..}[host home]$
[host home]$ cd ..
[host /]$
[host /]$ ls -la
{exit}

total 9999
---------- 27 root root 4096 Jan 26 2010 .
---------- 27 root root 4096 Jan 26 2010 ..
---------- 1 root root 0 Mar 14 19:16 .autojyk
---------- 1 root root 0 Feb 9 2009 .automan
---------- 1 root root 3550 May 14 2010 .bash_history
d--------- 2 root root 4096 Apr 26 04:02 put
d--------- 5 root root 4024 Apr 25 19:31 boot
[m[host /]$
[host /]$ exit
logout