1# The QDirStat File Age Statistics Window 2 3See also [GitHub issue #172](https://github.com/shundhammer/qdirstat/issues/172). 4 5QDirStat can break down the _age_ of files (based on their modification time) 6in a subtree by year and, for the current year and the year before, by 7months. This is strictly for files; directories, symlinks etc. are disregarded. 8 9This is a new view opened from the menu with _View_ -> _Show File Age 10Statistics_ or with the `F4` key. If a directory is selected, it starts with 11that directory, otherwise with the complete subtree. 12 13 14 15For each year, it shows: 16 17- The number of files that were last modified in that year 18 19- The percentage of those files relative to the selected subtree, both as a 20 percent bar and as a number 21 22- The total size of files that were last modified in that year 23 24- The percentage of those files relative to the selected subtree, both as a 25 percent bar and as a number. 26 27 28 29## Breaking Down to Months 30 31For the current year and the year before, you can expand the months (click on 32the little arrows on the left). 33 34 35 36 37## Directories with no Activity for some Years 38 39 40 41The list always starts with the current year, even if there was no activity in 42the subtree in that year (i.e. no file was modifed in that year). All inactive 43years up to the last year with any activity are displayed. 44 45This helps to quickly see at a glance that there was a while with no activity, 46even without reading the year numbers. 47 48 49## Drilling Down Deeper into Subdirectories 50 51Simply leave the _File Age Statistics_ window open and click on another 52directory in the main window's tree view, and the _File Age Statistics_ window 53is automatically updated with the data for that directory. 54 55You can also switch that behaviour off when you uncheck the _Sync with Main 56Window_ check box at that bottom of the _File Age Statistics_ window. In that 57case, you can always simply hit the `F4` key again to update the window. 58 59 60## Locating Files from that Year / Month 61 62If there are no more than 1000 files in the selected year or month, you can use 63the _Locate_ button to open another pop-up window that lists those files. Click 64on one of them to select it in the main window; the main window scrolls to that 65branch, selects the file and updates the _Details_ panel with it. 66 67This is limited to 1000 files because it becomes very unwieldy at some point, 68and performance suffers heavily. If you find yourself wanting to see more than 691000 files in a subtree, break it down to deeper subdirectories (see above). 70 71 72## Use Case 73 74This view was inspired by the discussion in 75[GitHub issue #165](https://github.com/shundhammer/qdirstat/issues/165) 76where an admin requested this for his users that had accumulated large amounts 77of data and lost their overview. 78 79It had become necessary to move some of those data to archive media, but the 80users had lost the overview what was current and what was not, i.e. which parts 81were good candidates to be moved to archive media. 82 83Imagine a large machine with a large storage array used by a great number of 84scientists collecting research data over many years. Researchers come and go; 85new ones take over their projects and their data for their research. Others 86leave when they are finished with their degree. Even with a best effort of 87documentation (which is wishful thinking to begin with), after some time it 88becomes murky what set of research data is what, and which of them are in 89active use. Somebody new will not dare to get rid of anything; even if that 90only means moving it to archive media where it's less easily accessible. 91 92While this _File Age Statistics_ is by no means a general solution, it can 93contribute to regain some kind of overview: If a directory branch has been 94completely unmodified for many years, this is an indication that it may not be 95in active use. 96 97Of course, this is not guaranteed: It is very well possible that they are 98actively using the data sets from 1995, 2000, this year and the year before, 99and the old data sets are a reference that does not change. Only the users can 100really tell. But the file age may give them additional hints. 101 102 103## Usage Hints 104 105It depends on the use case which columns in the _File Age Statistics_ are more 106important: The number of files in that year (or month) or their total 107size. That's why both of them are displayed. 108 109When it comes to the relevance of data in a subdirectory, the sheer number of 110files may be important: Even a lot of small files that accumulated may distract 111and get in the way, especially when scripting (`find` commands come to mind) 112over large directory trees. 113 114When that is not an issue, but disk space is running out, of course the total 115size of those files may be more important. 116 117One use case is showcased in 118[GitHub issue #172](https://github.com/shundhammer/qdirstat/issues/172): 119 120A photo collection that grew over the years. In that case, the number of files 121is much more important than their total size: During those years, camera 122technology rapidly advanced, moving from 3 Megapixels up to 10, then 12, then 12324. That means that photos taken in earlier years with considerably less 124Megapixels are of course much smaller, so for photo activity during those years 125the size is not a good measure; but the number of photos per year is. 126 127 128### Get an Overview Quickly 129 130Start at the top of the subtree. Arrange the windows so you can see both the 131important part of the main window and the _File Age Statistics_ window. 132 133If the _File Age Statistics_ for the toplevel don't give a good overview (which 134is likely), click on its first subdirectory in the main window's tree 135view. Watch the _File Age Statistics_ window. 136 137Then use the _Cursor Down_ key in the main window to go to the next 138subdirectory. Watch the _File Age Statistics_ window; but it's enough to give 139it just a glance: Watch how the inactive years (the greyed-out entries) 140change. Move to the next subdirectory etc.; you will now have a first 141impression on the age distribution among that first subdirectory level. 142 143If that also doesn't shed much light, go to the next deeper subdirectory level 144in the main window. Since the main window's tree view orders the directories by 145size by default, starting from the top is most promising. 146 147If repeating that over several subdirectory levels still doesn't give you an 148overview, this may not be the right tool for the job; it's not a catch-all 149solution for every situation. 150 151 152## Related Discovery Actions 153 154Don't forget that there are also actions in the _Discover_ menu to immediately 155find the oldest and the newest files in a directory tree. This is meant for 156individual (or at least small numbers) of very old or very new files. 157 158 159## Related Main Window Tree View Columns 160 161 162### Last Modified 163 164In the main window, the _Last Modified_ tree column shows the latest 165modification time in that subtree, but in _including_ directories and 166symlinks. That may or may not be what you need; it depends on the task. 167 168Notice that a directory's modification time is updated whenever a file is 169created or deleted there, or whenever a file is moved to or out of that 170directory. 171 172 173### Oldest File 174 175This may be little known since it is not enabled by default, but there is a 176similar column _Oldest File_ in the main window's tree view that shows the 177modification time of the oldest file (not directory, not symlink) in that 178subtree. This may be useful to drill down the tree view for very old files. 179 180To activate that column, switch to an appropriate main window layout 181(preferable L2 or L3), right-click on the headers of the tree view to open the 182context menu, then select _Hidden Colunns_ -> _Show Column "Oldest File"_. 183 184This functionality may be superseded by the relatively new _Show Oldest Files_ 185action in the _Discover_ menu. 186 187 188 189## Reference 190 191- [GitHub issue #172](https://github.com/shundhammer/qdirstat/issues/172) 192- [GitHub issue #165](https://github.com/shundhammer/qdirstat/issues/165) 193
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