C print file path from FILE*

Question

FILE * fd = fopen (\"/tmp/12345\",\"wb\");

If I have the variable fd , how can I print the file path ? (/tmp/12345) in Linux env.

Answer 1

You can't. Not with just standard C.

On Linux you can do:

#include 
#include 
#include 
#include 


int print_filename(FILE *f)
{
    char buf[PATH_MAX];
    char fnmbuf[sizeof "/prof/self/fd/0123456789"];
    sprintf(fnmbuf,"/proc/self/fd/%d", fileno(f));
    ssize_t nr;
    if(0>(nr=readlink(fnmbuf, buf, sizeof(buf)))) return -1;
    else buf[nr]='\0';
    return puts(buf);
}

int main(void)
{
    FILE * f = fopen ("/tmp/12345","wb");
    if (0==f) return EXIT_FAILURE;
    print_filename(f);

}