What happens to FILE pointer after file is closed?

Question

I wish to know what happens to FILE pointer after the file is closed. Will it be NULL?

Basically, I want to check if a file has already been closed before closing a

Answer 1

Peter Norvig quotes Auguste Comte (1798-1857):

  "Nothing is destroyed until it is replaced"

You could use the macro:

  #define fclose(fp)  ((fp) ? fclose(fp) : 0, (fp) = 0)

This fixes two different and opposing problems:

• The FILE * pointer is NULL'd after fclose, so it can't be fclose'd twice.

• This version of fclose will accept a NULL argument. Many common versions of fclose--such as those in HPUX, SGI, and CYGWIN--are happy with NULLs. It is odd that the FreeBSD-inspired versions such as in Linux, and Microsoft, aren't.

Of course, the macro introduces its own problems:

• It doesn't return the proper error value. But if you wanted to see this, you can disable the macro with extra parentheses, as in: if ((fclose)(fp) == EOF){ /* handle error... */ }

• It doesn't have function semantics, as it uses its argument multiple times. But it is hard to imagine this causing a problem. But you can use (fclose). Or name it FCLOSE, to follow convention.