c - 处理过多的路径分隔符

Question

我想知道与路径组件串联相关的问题，考虑到由于引入过多的斜线(如 "foo//bar")导致路径最终无效的特殊情况通过不正确的连接。

但是我随后注意到 Linux 上的一个奇怪行为。请参阅以下内容:

#include <stdio.h>

int main(void) {
    char buf[4];
    FILE *f = fopen("/tmp/bar", "w");
    fwrite("bar", 1, 3, f);
    fclose(f);
    f = fopen("/tmp////////bar", "r");
    if (f) {
        fread(buf, 1, 3, f);
        buf[3] = '\0';
        printf("%s\n", buf);
        fclose(f);
    }
    return 0;
}

上面的程序实际上打印了bar，这意味着"/tmp////////bar"被隐含地缩减为"/tmp/栏”。现在，这是标准行为吗？我可以依赖它吗？还是我仍然应该显式检查路径组件以确保它们的格式正确？

Answer 1

它是标准的(POSIX，2004):

3.266 Pathname

A character string that is used to identify a file. In the context of IEEE Std 1003.1-2001, a pathname consists of, at most, {PATH_MAX} bytes, including the terminating null byte. It has an optional beginning slash, followed by zero or more filenames separated by slashes. A pathname may optionally contain one or more trailing slashes. Multiple successive slashes are considered to be the same as one slash.

2013 年修订版有类似的措辞，但定义了确切的路径名 //(两个斜线，没有其他)实现。