UNIX keeps three times for each file: last modification, last inode change,
and last access.
Here are some things you can do with the last-access time:
-
Find files that have been forgotten.
This information comes from commands like
ls -lu
(
16.2
)
and
find -atime +180
(
17.5
)
.
(If you use the MH email system, you can find mail messages that haven't
been read or scanned in a long time.)
You can save disk space by cleaning up unused files; see article
23.19
.
-
Automatically
gzip
(
24.7
)
files to save disk space.
Some users run a shell script named
compresser
, which looks for
nonexecutable files that haven't been accessed in 90 days.
The program runs
gzip
on these files:
-perm -100
xargs
|
find
dir1 dir2
-type f ! -name '*.gz' ! -perm -100 -atime +90 -print | \
xargs gzip -v
|
A system like this could automatically archive files to tape and delete them.
It could have a personal "skip" list of files and directories to skip.
And so on...
-
Check a directory to see which files are being read by programs,
compilers, etc.
This "sanity check" can help you debug programs by confirming which files are
being accessed.
NOTE:
Some UNIX systems, including versions of BSD and SunOS, do not update
the access time of executable files (programs) when they're executed.
To test yours, use
ls -lu
on a pure-executable file (not a shell
script) before and after you run it.