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On 03/24/07 21:22, Roberto C. Sánchez wrote:
> On Sat, Mar 24, 2007 at 08:54:15PM -0500, Ron Johnson wrote:
>> On 03/24/07 20:45, CaT wrote:
>>> On Sat, Mar 24, 2007 at 08:38:54PM -0500, Ron Johnson wrote:
>>>>> However, realize that some programs create a file /tmp and then promptly
>>>>> unlink it, thus causing the file to take up space even though it does
>>>>> not have a directory entry.
>>>> How's that?
>>> UNIX does not deallocate disk space until all opens are closed.
>> Sure, if there are {hard,soft} links on the file. What if it's a
>> no-links file?
>>
> If there is still an open file descriptor, it will still be there. The
> disk space is only relinquished on the closing of all file descriptors.
>
> The following little C program will illustrate:
>
> #include <stdio.h>
> #include <stdlib.h>
>
> int main(void) {
> FILE *f;
>
> f = fopen("check_my_size", "w");
> int i;
> for (i = 0; i < 1000000; ++i)
> fprintf(f, "This is just filler for the file");
> system("ls -lk check_my_size");
> printf("Checking utilization:\n");
> fflush(stdout);
> system("df -k");
> sleep(2);
> printf("Unlinking file\n");
> fflush(stdout);
> unlink("check_my_size"); <<<<<<<<<
> system("ls -lk check_my_size");
> printf("Checking utilization:\n");
> fflush(stdout);
> system("df -k");
> sleep(2);
> printf("Closing file\n");
> fflush(stdout);
> fclose(f); <<<<<<<<<<<<
> system("ls -lk check_my_size");
> printf("Checking utilization:\n");
> fflush(stdout);
> system("df -k");
> return 0;
> }
>
Ah, you're deleting an open file!
The app, then, that deletes an open file is poorly written.
>
> You just need to compare the df output for the partition on which the
> program is running.
>
> Regards,
>
> -Roberto
- --
Ron Johnson, Jr.
Jefferson LA USA
Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!
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