在给定该文件的目录的情况下检查文件是否存在。怎么调试？

So basically I'm given a path to a directory and should return index.html if it exists or index.php if that file exists. The thing is that I don't know how to debug this function since I'm only implementing this function for a much larger program.

所以基本上我给了一个目录的路径，如果它存在则应该返回index.html或者如果该文件存在则返回index.php。问题是我不知道如何调试这个函数，因为我只是为一个更大的程序实现了这个函数。

char *indexes(const char *path) {
    char *newPath = malloc(sizeof(char) * strlen(path));
    strcpy(newPath, path);

    if (access(path, F_OK)) {
        if (access("index.html", F_OK)) {
            strcat(newPath, "/index.html");
        } else
        if (access("index.php", F_OK)) {
            strcat(newPath, "/index.php");
        } else {
            return NULL;
        }
    } else {
        return NULL;
    }
    return newPath;
}

Does this look correct? When I run my program I get an error of 501 Not Implemented

这看起来是否正确？当我运行我的程序时，我收到501未实现的错误

1 个解决方案

#1

Since you are going to concatenate path and /index.html into the newly allocated newPath, you must allocate it to at least the sum of lengths plus 1 extra byte for the null terminator:

由于您要将路径和/index.html连接到新分配的newPath，因此必须将其分配给至少长度之和加上空终止符的1个额外字节：

strlen(path) + strlen("/index.html") + 1;

"/index.php" is shorter than the other string, so the buffer can handle the alternative concatenation.

“/index.php”比其他字符串短，因此缓冲区可以处理备用连接。

The current code causes a buffer overflow, invoking undefined behavior, potentially causing the observed behavior.

当前代码导致缓冲区溢出，调用未定义的行为，可能导致观察到的行为。

Note that your code cannot work as written: you should concatenate before checking access, otherwise you check access in the wrong directory. You should also free(newPath); in case neither index file is found.

请注意，您的代码无法按照写入的方式工作：您应该在检查访问权限之前进行连接，否则您将检查错误目录中的访问权限。你也应该免费（newPath）;如果没有找到索引文件。

Here is a corrected version:

这是一个更正版本：

char *indexes(const char *path) {
    char *newPath = malloc(strlen(path) + strlen("/index.html") + 1);

    if (newPath) {
        strcpy(newPath, path);
        strcat(newPath, "/index.html");
        if (access(newPath, F_OK)) {
            return newPath;
        }
        strcpy(newPath, path);
        strcat(newPath, "/index.php");
        if (access(newPath, F_OK)) {
            return newPath;
        }
        free(newPath);
    }
    return NULL;
}

#1