From: Parkin Frank - fparki (fparki@acxiom.co.uk)
Date: Thu Aug 07 2003 - 08:21:21 EDT
Thanks go to Nikola Milutinovic and Joerg Bruehe.
Special thanks to Tim Cutts with this excellent response...
If you've created the file before, and it already exists, then creat()
truncates it rather than creating a new file. This means that the
atime() does not change. Consider the following program:
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
int main(void) {
int fd;
struct stat s;
fd = open("testfile", O_CREAT | O_WRONLY | O_TRUNC, 0644);
if (fd == -1) {
perror("Could not create file");
return 1;
}
if (fstat(fd, &s) != 0) {
perror("Could not fstat descriptor");
return 1;
}
if (write(fd, "some data\n", sizeof("some data\n")) == -1) {
perror("Could not write to file");
return 1;
}
printf("atime: %d\nctime: %d\nmtime: %d\n\n",
s.st_atime,
s.st_ctime,
s.st_mtime);
close(fd);
return 0;
}
This program creates a file, writes some data to it, and then reports
the atime ctime and mtime values.
The first time it's run, it produced the following output:
ecs2f:/nfs/acari/tjrc$ ./t
atime: 1060257520
ctime: 1060257520
mtime: 1060257520
all three the same. Fine.
Now, if I run the program again a few seconds later:
ecs2f:/nfs/acari/tjrc$ ./t
atime: 1060257520
ctime: 1060257573
mtime: 1060257573
Aha! The ctime and mtime have changed, but atime has not!
So, if this file you have is being created with creat() or with an
open() O_TRUNC flag as above, the file is not actually created anew, and
the atime on the inode does not change.
You need to actually unlink() the file between invocations of the
program for the atime to be updated.
-----Original Message-----
From: Parkin Frank - fparki
Sent: 07 August 2003 12:28
To: 'tru64-unix-managers@ornl.gov'
Subject: Bug in find command - tru64 v5.1a???
We use a find command in an automated process to delete
files.
find . -atime +7 -exec rm -ef {} ;\
The command has worked perfectly for several months.
However, last night it deleted 6 files that were in the process of being
written.
Is this correct behaviour?
Thanks
Frank
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