SSH read sometimes not working about libssh2-labview HOT 3 CLOSED

@Volinger, There are three "streams" to a shell: (1) standard input, stdin, (2) standard output, stdout, and (3) standard error, stderr. SSH is a "secure shell", so it also has these three streams if you establish a shell channel. The stdin stream is for sending data to a command. The Write VI are writing data to the stdin stream for the channel. The stdout stream is for reading the output from a command. The Read VI is reading from the stdout stream. Then, there is stderr, which by convention is used for displaying errors encountered while executing a command, but it is also sometimes used for displaying log messages, progress bars, or information that is not output of the command and should not be processed as data.

I suspect that you are not seeing any response because the command is writing to stderr instead of stdout. For example, the "qwer: command not found" response in PuTTY is probably from the stderr stream since it is an error and not output. Many, if not all, terminals, and terminal emulators like PuTTY, automatically read stdout and stderr from the shell and display them together in the terminal.

This toolkit is relatively low-level and does not provide for full-feature terminal for interacting with shells. This is a little out-of-scope for this project, but a full-feature terminal could be created using the building blocks of this toolkit.

I would try using the Read All Stderr.vi or the Read Stderr.vi in coordination with the Read VI. When you receive no response in stdout, is there content from reading stderr?

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@volks73 thank you very much for detailed answer! You are correct, the output which was eluding me was indeed stderr. With the Read Stderr.vi it is clearly visible. Glad to learn something new : )

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@Volinger Great! I glad I could help. It sounds like this question/issue has been answered/resolved, so I am will be closing it. Please open a new issue if you encounter anything else or you have another question.

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