Hey guys! Ever run into a head-scratcher where a command you know is installed just won't cooperate? I recently wrestled with this when using the command-stream library, specifically with the built-in which command. Let's dive into this little issue and how to get things working smoothly. We'll cover the problem, the steps to reproduce it, what's supposed to happen versus what actually happens, the environment where this occurs, a simple workaround, and some extra context to help you understand the nuances.

The Core Issue: which Giving the Cold Shoulder

So, the main problem? The built-in which command within command-stream is stubbornly returning a non-zero exit code, even when the command in question is sitting pretty in your system's PATH. This is a bummer because a non-zero exit code usually signals an error, making it seem like the command doesn't exist when, in reality, it totally does. This behavior can throw a wrench into your scripts, especially if you're using which to check for command availability before running them. Let's clarify this further by breaking down what happens, step by step.

Steps to Reproduce the Annoyance

To see this in action, let's use the gh CLI tool, which is the GitHub CLI, that's typically installed through Homebrew on macOS. Here's how you can replicate the problem:

1. Install gh: If you don't have it, install gh using Homebrew: brew install gh. This will set you up with the latest version of GitHub CLI.

2. Verify gh is Available: Open up your terminal and type gh --version. If everything's working as expected, you should see the gh CLI tool's version information printed out, meaning it's correctly installed and accessible.

3. Test command-stream's which: Now, let's use the command-stream library in your Node.js or Bun project. Here’s a snippet of code to illustrate:

   import { $ } from 'command-stream';
   
   const result = await 
   
   
   	
       
       
       
       
   	
   	
   	
   	
   	
   	
   	
       
       
       
       
       
       
       
       
       
       
   
   
       
   
           
       
       
   
           
   
               
   
                   
   
                       
   Fixing Command-stream's 'which' Command: A Guide
                       
   
                           Aug 15, 2025
                           by ADMIN
                           
                               49 views
                           
                       
                   
               
               
   
                   
   
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                           which gh`;
   console.log(result.code); // You'll likely see a non-zero value
   

   In this code, we're importing the $ function from command-stream. We then use it to execute the which gh command. The result.code property should ideally be 0, indicating success. However, you'll probably get a non-zero value instead. This is the core issue, and it shows that command-stream's which is misbehaving, at least in this scenario.

If you have followed all these steps carefully, you will successfully reproduce the issue and see the surprising behavior of command-stream's which command.

Expected vs. Actual: The Clash of Outcomes

Now, let's pinpoint what should happen versus what actually happens. Understanding this is crucial for knowing the extent of the problem.

• Expected Behavior: When you run which gh (or any existing command) using command-stream, the expected outcome is an exit code of 0. This signals that the command was found and is ready to run. The which command is designed to locate the executable file for a given command by searching through the directories listed in the PATH environment variable. When the command is found, which is supposed to return the full path to that command, and the exit code confirms that the command was successfully located.
• Actual Behavior: Unfortunately, the reality is different. Instead of 0, command-stream's which often returns a non-zero exit code. This indicates that the command wasn't found, even if the command is installed and accessible via the terminal (as proven by the gh --version test). This discrepancy is confusing and can lead to issues in scripts or automated processes that rely on which to verify command existence before execution. Because of this, the script will think the command does not exist and will cause further errors.

The Environment Where It All Goes Wrong

The issue is most prominent in a specific environment. Let's break it down:

• Operating System: The problem is particularly noticeable on macOS, specifically Darwin versions (like Darwin 24.5.0, as mentioned in the original report). macOS's unique file system structure and how it handles the PATH variable may play a role.
• command-stream Version: This bug affects the latest versions of command-stream. It's always a good idea to keep your libraries updated, but this issue seems to persist even with the most recent versions.
• Node.js/Bun: The issue occurs whether you're using Node.js or Bun (a fast JavaScript runtime). This suggests the problem lies within command-stream itself, and isn't necessarily related to the JavaScript runtime environment.

The Workaround: Staying Ahead of the Game

Fortunately, there's a straightforward workaround to keep your scripts running smoothly. If command-stream's which isn't playing nice, you can use a different approach.

• Leverage the System's which: You can use the system's own which command by bypassing command-stream's built-in function. This is typically the most reliable method, as the system's which is designed to correctly resolve the PATH and locate commands. You can do this using the sh function provided by command-stream, ensuring that it will use the system's installed which command.

  import { sh } from 'command-stream';
  const result = await sh('which gh', { mirror: false });
  console.log(result.code); // Should return 0 if gh is found
  

• Use --version: Another reliable method is to check if the command is working correctly by using the --version flag (or any other flag that produces output). This directly checks if the command can be executed and will return an exit code of 0 if everything is working fine.

  import { sh } from 'command-stream';
  const result = await sh('gh --version', { mirror: false });
  console.log(result.code); // Should return 0 if gh is installed
  

These workarounds are essential to ensure that your scripts don't fail unexpectedly because of the which command's behavior. They're simple to implement and provide a reliable way to verify command availability.

Additional Context: Homebrew and PATH Resolution

The root of the issue often lies in how command-stream handles PATH resolution, especially on systems with tools like Homebrew. Homebrew, a popular package manager on macOS, installs commands in directories like /opt/homebrew/bin. These directories are added to your PATH, making the commands accessible in your terminal.

However, it seems command-stream's built-in which might not always correctly interpret this PATH or correctly traverse all the directories, which results in the command not being found. Other built-in commands may have similar issues with PATH resolution on macOS systems with Homebrew.

Conclusion: Moving Forward

So, there you have it, guys! The built-in which command in command-stream can act a little funky, especially on macOS with Homebrew. By understanding the issue, how to reproduce it, and the workarounds, you can keep your scripts running smoothly. Always remember to test thoroughly and use the system's which or alternative methods to ensure command availability. Hopefully, this helps you avoid the same head-scratching moments I faced! Happy coding!