如何在Pike中获取文件扩展名？寻求类似Python endswith()的方法

Hey there! Let's tackle how to work with file extensions in Pike, whether you want to check if a filename ends with a specific suffix (like Python's endswith()) or extract the extension directly. Here are a couple of practical, straightforward approaches:

1. Extract the File Extension Directly #

If your goal is to pull the extension from a filename (e.g., get pdf from resume.pdf), you can use Pike's built-in string functions to find the last occurrence of the dot (.) and grab everything after it.

Here's a reusable function:

string get_file_extension(string filename) {
    int last_dot_pos = strrchr(filename, '.');
    // Handle edge cases: no dot, or dot is the first character (e.g., .bashrc)
    if (last_dot_pos <= 0) {
        return ""; // Return empty string if no valid extension exists
    }
    // Return everything after the last dot
    return substring(filename, last_dot_pos + 1);
}

// Test it out!
write(get_file_extension("project.docx") + "\n"); // Outputs: docx
write(get_file_extension("photo.png") + "\n");    // Outputs: png
write(get_file_extension(".gitignore") + "\n");   // Outputs: "" (adjust if you want to return gitignore)
write(get_file_extension("readme") + "\n");       // Outputs: ""

2. Implement a Python-Style endswith() Function #

If you just need to check if a filename ends with a specific suffix (e.g., is this a .txt file?), you can build a simple helper function that mimics Python's endswith() behavior.

bool string_endswith(string target, string suffix) {
    int target_len = strlen(target);
    int suffix_len = strlen(suffix);
    
    // If the suffix is longer than the target string, it can't match
    if (suffix_len > target_len) {
        return 0;
    }
    
    // Compare the end of the target string to the suffix
    return compare(substring(target, target_len - suffix_len), suffix) == 0;
}

// Test cases
write(string_endswith("logfile.txt", ".txt") ? "Yes\n" : "No\n");  // Yes
write(string_endswith("image.jpg", ".png") ? "Yes\n" : "No\n");    // No
write(string_endswith("archive.tar.gz", ".gz") ? "Yes\n" : "No\n");// Yes

Quick Notes #

• For filenames with multiple dots (like data.tar.gz), the first function will return the last segment after the final dot (which is usually what you want for file extensions).
• Adjust the edge case handling (like .bashrc) based on your specific needs—if you consider leading dots as valid extensions, just change the last_dot_pos <= 0 check to last_dot_pos == -1.

内容的提问来源于stack exchange，提问作者mIcHaL MiChAl