JSch: Is there a way to expose user environment va

I am trying to run commands which uses local Linux logical paths like cat $test_dir/test.dat, but the logical path $test_dir (which is a user environment variable) is not available via ChannelExec. But when I use interactive ChannelShell, I am able to see the user variables and the commands run fine on the interactive session. I can view system level environment variable only from "exec" session. Is that even possible using JSch library, if yes then how shall I achieve it and if not what library shall I use to achieve this?

Adding my class code below: `public class SecureShell {

private static final Logger logger = LogManager.getLogger(SecureShell.class);

private String uName;
private String pWord;
private String hName;
private int port;

private Session session = null;
private Channel channel = null;

/**Create an instance to start and stop the remote shell and execute commands remotely via java.
 * 
 * @param uName
 *          host username 
 * @param pWord
 *          host password
 * @param hName
 *          host name
 * @param port
 *          host port number
 */
public SecureShell(String uName, String pWord, String hName, int port) {
    this.uName = uName;
    this.pWord = pWord;
    this.hName = hName;
    this.port = port;
}

/**Create an instance to start and stop the remote shell and execute commands remotely via java.
 * 
 *@param uName
 *          host username 
 * @param pWord
 *          host password
 * @param hName
 *          host name
 */
public SecureShell(String uName, String pWord, String hName) {
    this.uName = uName;
    this.pWord = pWord;
    this.hName = hName;
    this.port = 22;
}

/**Start the session with the host.
 * @return
 *      true if the session started successfully, false otherwise
 */
public boolean startSession() {
    JSch jsch = new JSch();
    try {
        session = jsch.getSession(uName, hName, port);

        java.util.Properties config = new java.util.Properties();
        config.put("StrictHostKeyChecking", "no");
        session.setConfig(config);
        session.setPassword(pWord);
        session.connect();

    } catch (JSchException jsche) {
        logger.error(jsche.getMessage());
        return false;
    } 

    return true;
}

/** Execute commands on the host;
 * @param command
 *          command to be executed on the host.
 * @return
 *      status of the execution
 */
public int execute(String command) {

    int status = -1;
    if(session != null && session.isConnected()) {
        try {
            channel = session.openChannel("exec");
            //((ChannelExec)channel).setEnv("LC_XXX", "xxxxxxx");
            ((ChannelExec)channel).setPty(true);
            ((ChannelExec) channel).setCommand(command);

            InputStream in = channel.getInputStream();

            channel.connect();

             byte[] buffer = new byte[1024];
             while(true){
                 while(in.available()>0){
                     int i=in.read(buffer, 0, 1024);
                     System.out.print(new String(buffer, 0, i));
                     if(i<0)
                         break;
                }
                 if(channel.isClosed()){
                     if(in.available()>0) 
                         continue; 
                     status = channel.getExitStatus();
                     break;
                 }
            }
        } catch (JSchException jsche) {
            logger.error(jsche.getMessage());
        } catch (IOException ioe) {
            logger.error(ioe.getMessage());
        } finally {
            if(channel!=null && channel.isConnected())
                channel.disconnect();
        } 
    }

    return status;
}

/**Stop the session with the remote.
 * 
 */
public void stopSession() {

    if(session!=null && session.isConnected())
        session.disconnect();
}

public static void main(String[] args) {
    SecureShell ssh  = new SecureShell("user", "password", "hostname");
    ssh.startSession();
    System.out.println(ssh.execute("env"));
    ssh.stopSession();
}

回答1:

Since you're not opening up an interactive shell, your environment variables won't be set. However, you can use the bash command with --login (man bash for more details) to get the results you want

bash --login -c 'command arg1 ...'"

回答2:

The "exec" channel in the JSch (rightfully) does not allocate a pseudo terminal (PTY) for the session by default. As a consequence a different set of startup scripts is (might be) sourced. And/or different branches in the scripts are taken, based on absence/presence of the TERM environment variable. So the environment might differ from the interactive JSch "shell" session or when you use your SSH client.

Ways to fix this:

Fix your startup scripts to set the environment variables the same for both interactive and non-interactive sessions.
Another (not recommended) approach is to force the pseudo terminal allocation for the "exec" channel using the .setPty method:
```
Channel channel=session.openChannel("exec");
((ChannelExec)channel).setPty(true);
```
Using the pseudo terminal to automate a command execution can bring you nasty side effects. See for example
- Is there a simple way to get rid of junk values that come when you SSH using Python's Paramiko library and fetch output from CLI of a remote machine?
- Remove of unwanted characters when i am using jsch to run command
- Removing shell stuff (like prompts) from command output in JSch

For a similar issues, see

Certain Unix commands fail with "... not found", when executed through Java using JSch
Commands executed using JSch behaves differently than in SSH terminal (bypasses confirm prompt message of "yes/"no")