Question

To create a daemon I have read somewhere that in order to close all the open file descriptors we can use the following code:-

for (fd = 0; fd < _NFILE; fd++)
  close(fd); /* close all file descriptors */

I have to define _NFILE as

#define _NFILE 3

or is it already defined in some include files?
I tried to grep it in the /usr/include directory but could not find anything.

Answer 1

_NFILE only applies to original Unix. The portable way to do this is sysconf(_SC_OPEN_MAX) (POSIX).