[khaledh]

> A note on interpreters: If the executable file starts with a shebang (#!), the kernel will use the shebang-specified interpreter to run the program. For example, #!/usr/bin/python3 will run the program using the Python interpreter, #!/bin/bash will run the program using the Bash shell, etc.

This caused me a lot of pain while trying to debug a 3rd party Java application that was trying to launch an executable script, and throwing an IO error "java.io.IOException: error=2, No such file or directory." I was puzzled because I know the script is right there (using its full path) and it had the executable bit set. It turns out that the shebang in the script was wrong, so the OS was complaining (actual error from a shell would be "The file specified the interpreter '/foo/bar', which is not an executable command."), but the Java error was completely misleading :|

Note: If you wonder why I didn't see this error by running the script myself: I did, and it ran fine locally. But the application was running on a remote host that had a different path for the interpreter.

[1718627440]

Note, that this is not a Java specific problem, it can occur with other programs as well. "No such file or directory" is just the nice description for ENOENT, which can occur in a lot of syscalls. I typically just run the program through strace, then you will quickly see what the program did.

[gjf]

For those interested, I did a breakdown of the hashbang: https://blog.foletta.net/post/2021-04-19-what-the/

[mscdex]

Also be aware that kernel support for shebangs depends on CONFIG_BINFMT_SCRIPT=y being in the kernel config.