개요

• 솔라나라에 설명된 어플리케이션에 대해 맨 페이지를 찾아 출력한다.
• MAN 페이지에 대한 설명은 윈디하나의 솔라나라: MAN 페이지을 참고하자.
• svcadm(8)을 검색하려면 섹션에서 8 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.

closefrom(3c)

Standard C Library Functions                                     closefrom(3C)



NAME
       closefrom, fdwalk - close or iterate over open file descriptors

SYNOPSIS
       #include <stdlib.h>

       void closefrom(int lowfd);


       int fdwalk(int (*func)(void *, int), void *cd);

DESCRIPTION
       The  closefrom()  function  calls close(2) on all open file descriptors
       greater than or equal to lowfd.


       The effect of closefrom(lowfd) is the same as the code

         #include <sys/resource.h>
         struct rlimit rl;
         int i;

         getrlimit(RLIMIT_NOFILE, &rl);
         for (i = lowfd; i < rl.rlim_max; i++)
              (void) close(i);



       except that close() is called only on file descriptors that  are  actu‐
       ally  open, not on every possible file descriptor greater than or equal
       to lowfd, and close() is also  called  on  any  open  file  descriptors
       greater than or equal to rl.rlim_max (and lowfd), should any exist.


       The  fdwalk()  function  first  makes a list of all currently open file
       descriptors. Then for each file descriptor in the list,  it  calls  the
       user-defined  function,  func(cd,  fd),  passing  it the pointer to the
       callback data, cd, and the value of the file descriptor from the  list,
       fd.  The  list  is  processed  in  file  descriptor value order, lowest
       numeric value first.


       If func() returns a non-zero value, the iteration over the list is ter‐
       minated  and  fdwalk()  returns  the non-zero value returned by func().
       Otherwise, fdwalk() returns 0 after having called func() for every file
       descriptor in the list.


       The  fdwalk()  function  can  be used for fine-grained control over the
       closing of file descriptors. For example, the closefrom() function  can
       be implemented as:

         static int
         close_func(void *lowfdp, int fd)
         {
              if (fd >= *(int *)lowfdp)
                   (void) close(fd);
              return (0);
         }

         void
         closefrom(int lowfd)
         {
              (void) fdwalk(close_func, &lowfd);
         }



       The  fdwalk()  function  can  then  be used to count the number of open
       files in the process.

RETURN VALUES
       No return value is defined for closefrom(). If close() fails for any of
       the  open  file descriptors, the error is ignored and the file descrip‐
       tors whose close() operation failed might remain open  on  return  from
       closefrom().


       The  fdwalk() function returns the return value of the last call to the
       callback function func(), or 0 if  func()  is  never  called  (no  open
       files).

ERRORS
       No  errors  are  defined. The closefrom() and fdwalk() functions do not
       set errno but errno can be set by close() or by another function called
       by the callback function, func().

FILES
       /proc/self/fd    directory (list of open files)


USAGE
       The  act  of closing all open file descriptors should be performed only
       as the first action of a daemon process. Closing file descriptors  that
       are  in  use  elsewhere in the current process normally leads to disas‐
       trous results.

ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE VALUE _ MT-LevelUnsafe


SEE ALSO
       close(2),  getrlimit(2),  posix_spawn_file_actions_addclosefrom_np(3C),
       proc(5), attributes(7)



Oracle Solaris 11.4               9 Jul 2018                     closefrom(3C)