mtime, ctime, and atime Post: 302101136

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Top Forums UNIX for Beginners Questions & Answers Answers to Frequently Asked Questions Tips and Tutorials mtime, ctime, and atime Post 302101136 by Perderabo on Thursday 28th of December 2006 03:43:51 AM

12-28-2006

Administrator Emeritus

find command -mtime -ctime -atime

The find command uses arguments like:
-mtime -2
-mtime +2
-mtime 2

There are -ctime and -atime options as well. Since we now understand the differences among mtime, ctime, and atime, by understanding how find uses the -mtime option, the other two become understood as well. So I will describe find's use of the -mtime option.

As you probably know, the find command can run for minutes or hours depending on the size of the filesystem being searched. The find command makes a note of its own start time. It then looks at a file's mtime and computes how many seconds ago the file was modified. By dividing the seconds by 86,400 (and discarding any remainder), it can calculate the file's age in days:

Code:

0 days in seconds:       0  -   86399
1 day in seconds:    86400  -  172799
2 days in seconds:  172800  -  259159

So now that we know how many days ago a file was modified, we can use stuff like "-mtime 2" which specifies files that are 172800 to 259159 seconds older than the instant that the find command was started.

"-mtime -2" means files that are less than 2 days old, such as a file that is 0 or 1 days old.

"-mtime +2" means files that are more than 2 days old... {3, 4, 5, ...}

It may seem odd, but +0 is supposed to work and would mean files more than 0 days old. It is very important to recognize that find's concept of a "day" has nothing to do with midnight.

Last edited by Perderabo; 08-05-2007 at 12:40 PM..

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LEARN ABOUT REDHAT

tmpwatch

TMPWATCH(8)						   System Administrator's Manual					       TMPWATCH(8)

NAME

       tmpwatch - removes files which haven't been accessed for a period of time

SYNOPSIS

       tmpwatch [-u|-m|-c] [-faqstv] [--verbose] [--force] [--all] [--test]
		      [--fuser ] [--atime|--mtime|--ctime] [--quiet] <hours> <dirs>

DESCRIPTION

       tmpwatch  recursively  removes  files  which haven't been accessed for a given number of hours. Normally, it's used to clean up directories
       which are used for temporary holding space such as /tmp.

       When changing directories, tmpwatch is very sensitive to possible race conditions and will exit with an error if one is detected.  It  does
       not follow symbolic links in the directories it's cleaning (even if a symbolic link is given as its argument), will not switch filesystems,
	and only removes empty directories and regular files.

       By  default,  tmpwatch dates files by their atime (access time), not their mtime (modification time). If files aren't being removed when ls
       -l implies they should be, use ls -u to examine their atime to see if that explains the problem.

       If the --atime, --ctime or --mtime options are used in combination, the decision about deleting a file will be based on the maximum of this
       times.

       The hours parameter defines the threshold for removing files. If the file has not been accessed for hours hours, the file is removed.  Fol-
       lowing this, one or more directories may be given for tmpwatch to clean up.

OPTIONS

       -u, --atime
	      Make the decision about deleting a file based on the file's atime (access time). This is the default.

       -m, --mtime
	      Make the decision about deleting a file based on the file's mtime (modification time) instead of the atime.

       -c, --ctime
	      Make the decision about deleting a file based on the file's ctime (inode change time) instead of the atime;  for	directories,  make
	      the decision based on the mtime.

       -a, --all
	      Remove all file types, not just regular files and directories.

       -d, --nodirs
	      Do not attempt to remove directories, even if they are empty.

       -f, --force
	      Remove files even if root doesn't have write access (akin to rm -f).

       -t, --test
	      Doesn't remove files, but goes through the motions of removing them. This implies -v.

       -s, --fuser
	      Attempt to use the "fuser" command to see if a file is already open before removing it.  Not enabled by default.	 Does help in some
	      circumstances, but not all.  Dependent on fuser being installed in /sbin.

       -v, --verbose
	      Print a verbose display. Two levels of verboseness are available -- use this option twice to get the most verbose output.

SEE ALSO

       cron(1), ls(1), rm(1), fuser(1)

WARNINGS

       GNU-style long options are not supported on HP-UX.

AUTHORS

       Erik Troan <ewt@redhat.com>
       Preston Brown <pbrown@redhat.com>
       Nalin Dahyabhai <nalin@redhat.com>

4th Berkeley Distribution					  Wed Nov 28 2001						       TMPWATCH(8)