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SubjectRe: How can a process easily get a list of all it's open fd?
tricky. You can use /proc/<getpid>/fd, and close all
handles listed here, but this has some caveats:
it's _very_ slow if you have many open files.
it's not portable.
it's not safe if you have a thread/signal handler running.

i never heard of a right way to do this.

-alex

int close_all_fd()
{
char fdpath[PATH_MAX];
DIR * dp;
struct dirent * de;
int fd;
sprintf(fdpath, "/proc/%d/fd", getpid());
dp = opendir(fdpath);
if ( !dp )
return -errno;
while ( (de = readdir(dp)) )
{
if ( !strcmp(de->d_name, ".") || !strcmp(de->d_name, "..") )
continue;
fd = strtol(de->d_name, 0, 10);
if ( fd == dirfd(dp) || fd == 0 || fd == 1 || fd == 2 )
continue;
if ( close(fd) < 0 )
fprintf(stderr, "%s: %s\n", de->d_name, strerror(errno));
}
closedir(dp);
return 0;
}

On Tue, Aug 27, 2002 at 08:34:04AM -0700, Mark Atwood wrote:
>
> I need to close all the none std[in|out|err] open fd's.
>
> I've been told to do it like so:
>
> {
> int i;
> for (i=3; i<OPEN_MAX; i++)
> close(i);
> }
>
> This is very slow, plus I have discovered that I can have open fd's with
> values greater than OPEN_MAX.
>
> I thought about getting the max fd from rlimit, but that doesn't work
> either. Say I have a rlimit of 1024 open fd's, and I open numbers 3
> thru 1023, then I close 3 thru 1022, then I set the rlimit down to
> 16. rlimit then returns 16, but the largest open fd is still 1023.
>
> So that doesn't work.
>
> And I still have the problem that looping between 3 and whatever I pick
> as the top and calling close on each in turn is very slow.
>
> So what's the "right way" to do it?
>
> I would *love* for there to be an ioctl or some syscall that I could
> pass a pointer to an int and a pointer to an int array, and it would
> come back telling me how many open fd's I've got, and fill in the
> array with those fd's.
>
> --
> Mark Atwood | Well done is better than well said.
> mra@pobox.com |
> http://www.pobox.com/~mra
> -
-
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