SSH Connection with Remote Linux devices
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I have a shell script which should be run in rasberry pi which is a linux OS based system. I have tested in command prompt to ensure the file should be openable.
Microsoft Windows [Version 10.0.19045.3803] (c) Microsoft Corporation. All rights reserved. C:\Users\hp>ssh votpl@192.168.56.1 username@host password: Linux pi 6.1.21+ #1642 Mon Apr 3 17:19:14 BST 2023 armv6l The programs included with the Debian GNU/Linux system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/*/copyright. Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. Last login: Sat Jan 6 21:49:32 2024 from 192.168.56.100 Wi-Fi is currently blocked by rfkill. Use raspi-config to set the country before use. username@pi:~ $ cd Desktop username@pi:~/Desktop $ ./ROV.sh python: no process found No Arduino connection reset No ArduinoThis is the command prompt response for the ssh connection.Now , the file is opening via command prompt.Now,I want to automate this process..So,that on running a script in Qt..I should connect via ssh automatically at the backend.
How to script this process.I have used QProcess but it throws error like this:
SSH Error: "Process failed to start: The system cannot find the file specified.// SshHandler.cpp #include "SshHandler.h" #include "qdebug.h" SshHandler::SshHandler(QObject *parent) : QObject(parent) , sshProcess(new QProcess(this)) { } void SshHandler::connectToRemoteDevice(const QString &host, const QString &username, const QString &password) { // Assemble the SSH command QStringList sshArgs; sshArgs << "-T" << "ssh" << username + "@" + host << password << "cd Desktop && ./ROV.sh"; // Start the SSH process sshProcess->start("ssh", sshArgs); qDebug() << "SSH Error: " << sshProcess->errorString(); }@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
SSH Error: "Process failed to start: The system cannot find the file specified
Well, make sure the ssh executable can be found. For example you can use absolute path to ssh.exe
Also, you should not call errorString right after starting the process because start() is asynchronous. Better connect a slot to the error signal.
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@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
SSH Error: "Process failed to start: The system cannot find the file specified
Well, make sure the ssh executable can be found. For example you can use absolute path to ssh.exe
Also, you should not call errorString right after starting the process because start() is asynchronous. Better connect a slot to the error signal.
And why is sh needed here at all? Start ssh directly.
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And why is sh needed here at all? Start ssh directly.
@Christian-Ehrlicher ok edited..But,even though im running it shows, SSH Error: "Unknown error".
I don't know the correct command line arguments..can someone guide me please
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@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
SSH Error: "Process failed to start: The system cannot find the file specified
Well, make sure the ssh executable can be found. For example you can use absolute path to ssh.exe
Also, you should not call errorString right after starting the process because start() is asynchronous. Better connect a slot to the error signal.
@jsulm like this?
connect(sshProcess, &QProcess::readyReadStandardOutput, this, &SshHandler::onSshReadyReadStandardOutput); connect(sshProcess, &QProcess::readyReadStandardError, this, &SshHandler::onSshReadyReadStandardError); -
@jsulm like this?
connect(sshProcess, &QProcess::readyReadStandardOutput, this, &SshHandler::onSshReadyReadStandardOutput); connect(sshProcess, &QProcess::readyReadStandardError, this, &SshHandler::onSshReadyReadStandardError);I doubt the password can be passed on the command line. Take a look on how to pass a password to ssh but for sure it's not as a simple argument.
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@jsulm like this?
connect(sshProcess, &QProcess::readyReadStandardOutput, this, &SshHandler::onSshReadyReadStandardOutput); connect(sshProcess, &QProcess::readyReadStandardError, this, &SshHandler::onSshReadyReadStandardError);@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
like this?
Did you see https://doc.qt.io/qt-6/qprocess.html#errorOccurred ?
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I doubt the password can be passed on the command line. Take a look on how to pass a password to ssh but for sure it's not as a simple argument.
@Christian-Ehrlicher yes..i thought that too.when i gone through examples,they have said sshpass for automating the authentication.But,I need to know that is that only problem..I dont know how the QProcess take the arguments..Im doubtful about the argument list. Although classes like TCP socket and sslsocket used to networking,but i dont know whether they could access passwords too.In Qt kits..There is an option for ssh feature but don't know that very well
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@Christian-Ehrlicher yes..i thought that too.when i gone through examples,they have said sshpass for automating the authentication.But,I need to know that is that only problem..I dont know how the QProcess take the arguments..Im doubtful about the argument list. Although classes like TCP socket and sslsocket used to networking,but i dont know whether they could access passwords too.In Qt kits..There is an option for ssh feature but don't know that very well
@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
I dont know how the QProcess take the arguments..I
I don't see what this has to do with the password problem - you provide wrong arguments to ssh, ssh bails out with
Unknown error- everything else would be surprising. Also ssh for sure does not simply take an argumentcd Desktop && ./ROV.shwhich is executed after the login.
You first have to inform you about the correct ssh parameters for your task. No Qt problem here. -
@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
I dont know how the QProcess take the arguments..I
I don't see what this has to do with the password problem - you provide wrong arguments to ssh, ssh bails out with
Unknown error- everything else would be surprising. Also ssh for sure does not simply take an argumentcd Desktop && ./ROV.shwhich is executed after the login.
You first have to inform you about the correct ssh parameters for your task. No Qt problem here.@Christian-Ehrlicher Yes of course..that's what i have said that i have doubtful about the arguments..i dont know how to give the arguments likewise in command line. There is no Qt documentation for this.
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@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
I dont know how the QProcess take the arguments..I
I don't see what this has to do with the password problem - you provide wrong arguments to ssh, ssh bails out with
Unknown error- everything else would be surprising. Also ssh for sure does not simply take an argumentcd Desktop && ./ROV.shwhich is executed after the login.
You first have to inform you about the correct ssh parameters for your task. No Qt problem here.@Christian-Ehrlicher So even before im trying to read the file in the remote directory,i want to ensure that whether it is connected or not by just giving hostname and username but im receiving this:
SSH Error: "ssh: connect to host port 22: Connection refused\r\n"
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@Christian-Ehrlicher So even before im trying to read the file in the remote directory,i want to ensure that whether it is connected or not by just giving hostname and username but im receiving this:
SSH Error: "ssh: connect to host port 22: Connection refused\r\n"
@Vijaykarthikeyan You should not use passwords but identity files, then there is no need to provide password.
"ssh: connect to host port 22: Connection refused" - this means that there is no SSH server listening on port 22 on that machine, again nothing Qt specific.
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@Vijaykarthikeyan You should not use passwords but identity files, then there is no need to provide password.
"ssh: connect to host port 22: Connection refused" - this means that there is no SSH server listening on port 22 on that machine, again nothing Qt specific.
@jsulm are the key files to be located on both client and server sides? or from development side?in Qt tools,there is an option for ssh connection
can i refer this.
https://doc.qt.io/qtcreator/creator-developing-generic-linux.html(or)
can we use sshpass which is helpful for scripting? -
@jsulm are the key files to be located on both client and server sides? or from development side?in Qt tools,there is an option for ssh connection
can i refer this.
https://doc.qt.io/qtcreator/creator-developing-generic-linux.html(or)
can we use sshpass which is helpful for scripting?@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
can i refer this.
What you're doing is not related to QtCreator.
Not QtCreator is accessing the device via SSH but your application using QProcess and ssh executable. You need to generate a key file and upload it to your device, see for example https://askubuntu.com/questions/46930/how-can-i-set-up-password-less-ssh-login -
@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
can i refer this.
What you're doing is not related to QtCreator.
Not QtCreator is accessing the device via SSH but your application using QProcess and ssh executable. You need to generate a key file and upload it to your device, see for example https://askubuntu.com/questions/46930/how-can-i-set-up-password-less-ssh-login@jsulm ok..thank you ..working..I have successfully run the remote linux device via command line terminal
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@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
can i refer this.
What you're doing is not related to QtCreator.
Not QtCreator is accessing the device via SSH but your application using QProcess and ssh executable. You need to generate a key file and upload it to your device, see for example https://askubuntu.com/questions/46930/how-can-i-set-up-password-less-ssh-login@jsulm Now,I have the key and i tested in command terminal and it works well. Now,i don't know the command line arguments for linux to be used in QProcess. when goes through the documentation,it says the start function takes command line arguments but not mentioned the correct format. Can someone guide me how to use the command line arguments for linux to be run correctly in QProcess.It should open the file in desktop directory after connecting with the linux host
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@jsulm Now,I have the key and i tested in command terminal and it works well. Now,i don't know the command line arguments for linux to be used in QProcess. when goes through the documentation,it says the start function takes command line arguments but not mentioned the correct format. Can someone guide me how to use the command line arguments for linux to be run correctly in QProcess.It should open the file in desktop directory after connecting with the linux host
@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
not mentioned the correct format
What does this mean? You don't need to re-format the arguments in any way. Just pass them to QProcess::setArguments(). The detailed description also has an example on how to pass arguments.
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@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
not mentioned the correct format
What does this mean? You don't need to re-format the arguments in any way. Just pass them to QProcess::setArguments(). The detailed description also has an example on how to pass arguments.
@Christian-Ehrlicher ok..when i included this after starting the process:
qDebug() << sshProcess->state(); qDebug() << "SSH Output:" << sshProcess->readAllStandardOutput(); qDebug() << "SSH Error Output:" << sshProcess->readAllStandardError();it gives like this:
QProcess::Running
SSH Output: ""
SSH Error Output: ""why?it is not printing..readAllStandardOutput and readAllStandardError are QBytArrays..
Can I consider this as my program executed correctly?
Because on terminal, when successfully connected and executing the shell scirpt..it runs like this:
python: no process found
No Arduino
connection reset
No Arduino
connection reset
No ArduinoIn my Qt,it should print like this
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@Christian-Ehrlicher ok..when i included this after starting the process:
qDebug() << sshProcess->state(); qDebug() << "SSH Output:" << sshProcess->readAllStandardOutput(); qDebug() << "SSH Error Output:" << sshProcess->readAllStandardError();it gives like this:
QProcess::Running
SSH Output: ""
SSH Error Output: ""why?it is not printing..readAllStandardOutput and readAllStandardError are QBytArrays..
Can I consider this as my program executed correctly?
Because on terminal, when successfully connected and executing the shell scirpt..it runs like this:
python: no process found
No Arduino
connection reset
No Arduino
connection reset
No ArduinoIn my Qt,it should print like this
@Vijaykarthikeyan Now,it ic successfully connected,
SSH Output: "Linux pi 6.1.21+ #1642 Mon Apr 3 17:19:14 BST 2023 armv6l\n\nThe programs included with the Debian GNU/Linux system are free software;\nthe exact distribution terms for each program are described in the\nindividual files in /usr/share/doc/*/copyright.\n\nDebian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent\npermitted by applicable law.\n\nWi-Fi is currently blocked by rfkill.\nUse raspi-config to set the country before use.\n\n"
But,when i give the command to navigate to the file directory it says too many arguments
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@Christian-Ehrlicher ok..when i included this after starting the process:
qDebug() << sshProcess->state(); qDebug() << "SSH Output:" << sshProcess->readAllStandardOutput(); qDebug() << "SSH Error Output:" << sshProcess->readAllStandardError();it gives like this:
QProcess::Running
SSH Output: ""
SSH Error Output: ""why?it is not printing..readAllStandardOutput and readAllStandardError are QBytArrays..
Can I consider this as my program executed correctly?
Because on terminal, when successfully connected and executing the shell scirpt..it runs like this:
python: no process found
No Arduino
connection reset
No Arduino
connection reset
No ArduinoIn my Qt,it should print like this
@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
why?it is not printing..readAllStandardOutput and readAllStandardError
As I presume you have discovered, you will not receive any output from a subprocess if you ask for it immediately after starting it --- no output has yet been produced. You either need to
connect()toreadyRead.,.,.(), callwaitForReadyRead()(yuck!) or wait until process finished.But,when i give the command to navigate to the file directory it says too many arguments
For people to help you, don't you think we need to see what "command" you are issuing, how you are issuing it, and just what the error message reads? Or do you think we can tell you what is wrong with your "command to navigate to the file directory" without knowing what you have done?
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@Vijaykarthikeyan said in SSH Connection with Remote Linux devices:
why?it is not printing..readAllStandardOutput and readAllStandardError
As I presume you have discovered, you will not receive any output from a subprocess if you ask for it immediately after starting it --- no output has yet been produced. You either need to
connect()toreadyRead.,.,.(), callwaitForReadyRead()(yuck!) or wait until process finished.But,when i give the command to navigate to the file directory it says too many arguments
For people to help you, don't you think we need to see what "command" you are issuing, how you are issuing it, and just what the error message reads? Or do you think we can tell you what is wrong with your "command to navigate to the file directory" without knowing what you have done?
