There’s an old riddle in Unix circles: “Name a letter that is not an option for the ls command”. The advent of the GNU version of ls has only made this more difficult to answer. Even if you’re a Unix/Linux power user, you’ve probably only memorized a small handful of the available options.
For example, I have “ls -lArt” burned into my brain from my Sys Admin days. “-l” for detailed listing, “-A” to show hidden files and directories (but not the “.” and “..” links like “-a“), sort by last modified time with “-t“, and “-r” to reverse the sort so the newest files appear right above your next shell prompt.
$ ls -lArt
total 1288
-rw-r--r-- 1 root root 9 Aug 7 2006 host.conf
-rw-r--r-- 1 root root 433 Aug 23 2020 apg.conf
-rw-r--r-- 1 root root 26 Dec 20 2020 libao.conf
-rw-r--r-- 1 root root 12813 Mar 27 2021 services
-rw-r--r-- 1 root root 769 Apr 10 2021 profile
-rw-r--r-- 1 root root 449 Nov 29 2021 mailcap.order
-rw-r--r-- 1 root root 119 Jan 10 2022 catdocrc
...
-rw-r--r-- 1 root root 52536 Feb 23 11:44 mailcap
-rw-r--r-- 1 root root 108979 Mar 2 09:24 ld.so.cache
-rw-r--r-- 1 root root 75 Mar 3 18:08 resolv.conf
drwxr-xr-x 5 root lp 4096 Mar 5 19:52 cups
You’ll note that the timestamps are displayed in two different formats. The oldest files show “month day year”, while the newer files show “month day hh:mm”. The default for ls is that files more than six months old display year information.
Personally I prefer consistent ISO-style timestamps with “--time-style=long-iso“:
$ ls -lArt --time-style=long-iso
total 1288
-rw-r--r-- 1 root root 9 2006-08-07 13:14 host.conf
-rw-r--r-- 1 root root 433 2020-08-23 10:52 apg.conf
-rw-r--r-- 1 root root 26 2020-12-20 11:21 libao.conf
-rw-r--r-- 1 root root 12813 2021-03-27 18:32 services
-rw-r--r-- 1 root root 769 2021-04-10 16:00 profile
-rw-r--r-- 1 root root 449 2021-11-29 08:07 mailcap.order
-rw-r--r-- 1 root root 119 2022-01-10 19:08 catdocrc
...
-rw-r--r-- 1 root root 52536 2026-02-23 11:44 mailcap
-rw-r--r-- 1 root root 108979 2026-03-02 09:24 ld.so.cache
-rw-r--r-- 1 root root 75 2026-03-03 18:08 resolv.conf
drwxr-xr-x 5 root lp 4096 2026-03-05 19:52 cups
While “-t” sorts on last modified time by default, other options allow you to sort and display other timestamps. For example, “-u” sorts on and displays last access time. “-u” is hardly memorable as last access time, but remember “-a” is used for something else.
It’s a pain trying to remember the one letter options for the other timestamps– and note there isn’t even a short option for sorting/displaying on file creation time. So I just use “--time=” to pick the timestamp I want:
$ ls -lArt --time=birth --time-style=long-iso
total 1288
-rw-r--r-- 1 root root 1013 2025-04-10 10:27 fstab
drwxr-xr-x 2 root root 4096 2025-04-10 10:27 ImageMagick-6
drwxr-xr-x 2 root root 4096 2025-04-10 10:27 GNUstep
...
-rw-r--r-- 1 root root 142 2026-02-23 11:41 shells
-rw-r--r-- 1 root root 52536 2026-02-23 11:44 mailcap
-rw-r--r-- 1 root root 108979 2026-03-02 09:24 ld.so.cache
-rw-r--r-- 1 root root 75 2026-03-03 18:08 resolv.conf
Here we’re sorting on and displaying file creation times (“--time=birth“). You can use “--time=atime” or “--time=ctime” for the other timestamps.
If this command line seems long and unwieldy, remember that you can create aliases for commands in your .bashrc or other startup files:
alias ls='ls --color=auto --time-style=long-iso'
alias lb='ls -lArt --time=birth'
With normal ls commands, I’ll get colored output always, and “long-iso” dates whenever I use “-l“. I can use lb whenever I want file creation times. Note that alias definitions “stack”– the “lb” alias will get the color and time-style options from my basic “ls” alias, so I don’t need to include the “--time-style” option in the “lb” alias.
Righteous IT 