Question

Say i open up /dev/ttyUSB0. Now i want to use its file descriptor to get its filepath.

int myfd;

int main(int argc, char *argv[]){
char linkname[256];
ssize_t r;

myfd = open("/dev/ttyUSB0", O_RDWR);
if(myfd<0){

    perror("open error");
    exit(1);
}

r = readlink("/proc/self/fd/myfd", linkname, sizeof(linkname)-1);

if(r<0){
    perror("lstat");
    exit(EXIT_FAILURE);
}

printf("%s\n", linkname);

close(myfd);

    return 0;
}

What i should be getting is /dev/ttyUSB0.. Am i doing it the wrong way?

Answer 1

Surely the string myfd isn’t in the /proc filesystem? I think the link is named numerically, so you need the value of the variable myfd in the call to readlink().