svcadm(8)을 검색하려면 섹션에서 8 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.
closefrom(3c)
closefrom(3C) Standard C Library Functions closefrom(3C)
NAME
closefrom, fdwalk - close or iterate over open file descriptors
SYNOPSIS
#include <unistd.h>
void closefrom(int lowfd);
#include <stdlib.h>
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, us‐
ing an undocumented fcntl() command.
The fdwalk() function first makes a list of all currently open file de‐
scriptors. 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 nu‐
meric 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-LevelSee below
MT-Level
The fdwalk() function is Unsafe.
The closefrom() function is Async-Signal-Safe.
SEE ALSO
close(2), fcntl(2), getrlimit(2), posix_spawn_file_actions_addclose‐
from_np(3C), proc(5), attributes(7)
HISTORY
A function prototype for closefrom() was added to <unistd.h> in Oracle
Solaris 11.4.72.
The closefrom() function was made Async-Signal-Safe in Oracle Solaris
11.3.31. Prior to that it had an MT-Level of Unsafe.
The closefrom() function and fdwalk() functions were introduced in So‐
laris 9, with function prototypes in <stdlib.h> for both.
Oracle Solaris 11.4 13 Sep 2024 closefrom(3C)