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;
}
You just need to compare the df output for the partition on which the
program is running.
Regards,
-Roberto
--
Roberto C. Sánchez
http://people.connexer.com/~roberto
http://www.connexer.com
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