Why Does JSch Throw a 'Command not found' Error When Executing Unix Commands, and How Can I Fix It?-javaTutorial-php.cn

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Why Does JSch Throw a 'Command not found' Error When Executing Unix Commands, and How Can I Fix It?

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Nov 14, 2024 am 11:16 AM

Why Does JSch Throw a

Troubleshooting "Command not found" Errors When Executing Unix Commands Through Java with JSch

Problem:

Java code using JSch fails to execute certain Unix commands with a "command not found" error, despite being able to execute other simple commands successfully. Specifically, running an Ab-initio graph through Java using the "air sandbox run" command gives the error.

Possible Cause:

The JSch "exec" channel does not allocate a pseudo terminal (PTY) by default, resulting in a different set of startup scripts being sourced or different branches in scripts being taken based on the absence of the TERM environment variable. As a result, the environment may differ from an interactive SSH session, potentially leading to a PATH issue.

Solutions:

Fix the command: Use a full path to the "air" executable in the command string to avoid relying on the PATH environment variable.
Fix startup scripts: Make sure startup scripts set the PATH the same for both interactive and non-interactive sessions.
Use a login shell: Run the command through a login shell (with the "--login" switch) to inherit the current user's environment.
Modify the environment: Change the PATH environment variable within the command string to include the path to the "air" executable.
Force PTY allocation (not recommended): Enable pseudo terminal allocation for the "exec" channel using the setPty(true) method. However, this can lead to unintended consequences or side effects.

Additional Notes:

Disabling the pseudo terminal allocation in an SSH client can reproduce the error.
Other similar issues include commands behaving differently in JSch than in SSH terminals and difficulties exposing user environment variables to the "exec" channel.

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