如何在Q语言（kdb）中获取当前运行文件路径，类似Python的__file__？

Great question! Unlike Python which has the handy __file__ attribute built-in, Q/kdb+ doesn't offer a direct out-of-the-box equivalent. But don't worry—there are several reliable workarounds to fetch the path of your currently running script. Let's walk through them:

Method 1: Parse .z.s (For Scripts Loaded with \l) #

When you load a script using the \l (load) command (e.g., \l my_script.q), the .z.s system variable returns the current execution expression. We can parse this to extract the script path:

// Inside your script file
script_path: first " " vs first 1 _ string .z.s

How it works: #

• .z.s will return a value like `\\l /full/path/to/your/script.q` when the script is loaded.
• Converting it to a string, stripping the first character (the backtick), splitting on spaces, and taking the second element gives you the full script path.

Method 2: Use System Process Info (More Reliable, Cross-Platform) #

This method leverages system commands to fetch the Q process's command-line arguments, which includes the script path if the script was launched via q script.q or loaded in a way that's part of the process args.

For Linux/macOS: #

script_path: first 1 _ " " vs first system "ps -p ", string .z.pid, " -o args="

For Windows: #

script_path: first 1 _ " " vs first system "wmic process where processid=", string .z.pid, " get commandline | findstr /v CommandLine"

How it works: #

• .z.pid gives you the current Q process ID.
• We use system commands (ps on Unix-like systems, wmic on Windows) to get the command line that started the process.
• Splitting the result and taking the second element skips the q/q.exe executable name, leaving the script path.

Method 3: Wrap It in a Cross-Platform Function #

To avoid writing OS-specific code every time, you can create a reusable function that handles both Unix-like and Windows systems:

get_script_path:{
    $[
        .z.os=`w;  // Check if running on Windows
        first 1 _ " " vs first system "wmic process where processid=", string .z.pid, " get commandline | findstr /v CommandLine";
        first 1 _ " " vs first system "ps -p ", string .z.pid, " -o args="
    ]
}

Just call get_script_path[] anywhere in your script to get the full path.

Important Notes: #

• These methods work best when your script is run as a file (either via q script.q or loaded with \l). In an interactive Q session where you're typing commands directly, they'll return empty or irrelevant values since there's no script file involved.
• If your script is loaded from a relative path, the returned path will reflect that—you can use .z.p (current working directory) to convert it to an absolute path if needed.

内容的提问来源于stack exchange，提问作者user983716