Recently, I encountered a strange issue when executing the binary file ‘protoc’, which reported the error no such file or directory: ./protoc. The file was clearly there, yet it kept reporting this error. Could it be a system bug? Whenever encountering bizarre issues, we tend to suspect the operating system or compiler, but often we end up being the fool. This time was no exception; after continuous attempts, I discovered that this was actually a system feature.

Strange error: No such fileStrange error: No such file

In fact, if you’re a novice encountering this problem for the first time, you’d be at a loss, with no idea how to troubleshoot. Before continuing to read, you might want to guess what could cause this error when executing a binary file.

Search Engine’s Answer

The binary file actually exists, and the permissions are correct, yet it still reports an error when executed. Encountering this problem for the first time, I had no troubleshooting ideas at all. It seemed like something that shouldn’t happen.

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$ ./protoc
zsh: no such file or directory: ./protoc
$ ls -alh protoc
-rwxr-xr-x 1 test users 1.1M Jun 17 10:20 protoc

Before ChatGPT, when faced with an unsolvable problem, we would first turn to search engines. Searching for no such file or directory but file exist yields many results:

Google search results: no such file or directoryGoogle search results: no such file or directory

The first result here, No such file or directory? But the file exists!, matches my problem quite well. In the top-voted answer to the question, the conclusion is given right away: it might be due to running a 32-bit binary on a 64-bit machine that doesn’t support 32-bit environments. Specifically for my binary file, it was indeed copied from an old machine and executed on a 64-bit machine. We can use the file command to check the file format, with the following result:

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$ file protoc
protoc: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 2.6.4, stripped

It seems this is indeed the cause, but why does it result in this error? How did others troubleshoot to find this cause? The answer found through the search engine only gives the conclusion, without providing specific troubleshooting steps or explaining the root cause of the problem. To dig deeper, one would need to change keywords and continuously try to delve into more pages.

Dialogue with ChatGPT

Since the advent of ChatGPT, my first reaction when encountering a problem is to ask ChatGPT. For this issue, I directly pasted the command error to ChatGPT and asked why it’s telling me the file doesn’t exist when it clearly does and has the correct permissions. ChatGPT then provided several troubleshooting directions, which upon initial review, didn’t seem to be the issue. I continued to ask:

Are there any other methods to troubleshoot this problem?

ChatGPT listed many more troubleshooting directions, one of which seemed very insightful - Debug with strace: Use strace ./protoc to trace system calls and see if any errors occur during execution. I knew about the strace command and had used it before, but I hadn’t thought of using strace to trace this problem. After ChatGPT’s hint, I ran it and indeed found an error:

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$ strace -f ./protoc
execve("./protoc", ["./protoc"], 0x7fff2cd172f8 /* 40 vars */) = -1 ENOENT (No such file or directory)
strace: exec: No such file or directory
+++ exited with 1 +++

It appears that the execve command returned ENOENT, which is the root cause of the command line execution error. I then pasted this error directly to ChatGPT for further explanation. The result was quite good, with ChatGPT providing a comprehensive explanation: The strace output shows that the execve system call failed. execve is used to execute a program, in this case trying to execute ./protoc. There could be several reasons for not finding the file, such as:

  • Architecture mismatch: If protoc was compiled for a different hardware architecture (e.g., running a 32-bit program on a 64-bit system without necessary library support), it could cause this error.
  • Dynamic library issues: If dynamic libraries (.so files) that protoc depends on are missing or have incorrect paths, it could also cause this problem. You can use ldd ./protoc to check dependencies.

Then, I asked ChatGPT to provide specific methods to verify these guessed causes, and the result was as follows:

ChatGPT's answer about the cause of the "No such file" errorChatGPT's answer about the cause of the "No such file" error

So there’s one last question: Why does running a 32-bit program on a 64-bit system without necessary library support result in this error? Is there any documentation that explains this situation? I asked ChatGPT, but it didn’t provide detailed document sources, only offering some of its own explanations: By default, many 64-bit systems may not have 32-bit compatibility libraries pre-installed because modern software is primarily 64-bit. If you try to run a 32-bit program, the system needs these 32-bit versions of libraries. If these libraries don’t exist, the operating system’s loader can’t load the 32-bit dynamic libraries required by the program, causing the execution to fail and return a “No such file or directory” error.

execve Documentation

Although ChatGPT didn’t find relevant explanations from documentation, since we’ve identified that it’s an execve error, we can directly read the man manual. Searching for the error code ENOENT in the manual, we find the following explanation:

ENOENT: The file pathname or a script or ELF interpreter does not exist.

If the executable is a dynamically linked ELF executable, the interpreter named in the PT_INTERP segment is used to load the needed shared objects. This interpreter is typically /lib/ld-linux.so.2 for binaries linked with glibc (see ld-linux.so(8)).

We can see that this error is reported because there is no ELF interpreter in my current 64-bit machine environment. At this point, we’ve finally fully understood the root cause of this error.

Conclusion

In facing this bizarre problem, search engines, ChatGPT, and personal efforts each played indispensable roles. Search engines like Google provide a vast pool of information, allowing us to quickly access various possible solutions and historical cases. However, the limitation of search engines is that they usually only provide ready-made information rather than customized advice for specific situations.

ChatGPT, on the other hand, is more interactive and targeted in providing solutions. It can offer more customized solutions based on specific problems, help narrow down the range of solutions, and provide guidance on logic and steps during the troubleshooting process. In the future, ChatGPT should gradually replace search engines and become the greatest assistant for individuals.