linux中的stat systecall返回错误

Question

I am using RHEL 4

i am using syscall stat as follows:-

if (stat ("file",&stat_obj)){

     if (errno == ENOENT){
        printf("File not found");
     }else{
        printf("Unexpected error occured %d ",errno);
     }
}

sometimes i get error message as ""Unexpected error occured 0"

That means i get error as "0" . i checked file permissions that are ok

what does that mean? I am not able to understand why sometimes this is happening ?

Any suggestions?

Answer 1

Does it give you any meaningful error message if you call it like this?

   if (stat("file", &stat_obj) == -1) {
       perror("stat");
   }

Answer 2

Do you have a signal handler in your program? If so, and it may affect errno , then make sure that it saves errno on entry and restores it to its original value before returning.

Also ensure that you #include <errno.h> , and are not declaring errno yourself, especially if your program is multithreaded. errno is a per-thread variable so if you declare it as a global you can get the wrong one. (On some platforms you sometimes also need a special compilation flag like -D_TS_ERRNO for thread-safe errno, but no such flag is needed on Linux.)