How to sort Linux ls command file output

A couple of days ago I was asked how to sort the output from the Unix and Linux ls command. Off the top of my head I knew how to sort the ls output by file modification time, and also knew how to sort ls with the Linux sort command, but I didn't realize there were other cool file sorting options available until I looked them up.

In this short tutorial I'll demonstrate the Unix/Linux ls command file sorting options I just learned.

Sort Linux ls output by file modification time

To help us get rolling, here are two quick examples that show how to sort ls command output by file modification time.

First, to sort the ls command output by file modification time, in order from the most recently-modified file (newest) to the oldest, use this ls command:

ls -lt

This results in output similar to the following:

$ ls -lt

total 8448
drwx------+  46 al  al     1564 Oct 22 11:48 Desktop
drwx------+  25 al  al      850 Oct 18 17:49 Downloads
drwx------+ 224 al  al     7616 Oct 15 20:13 Pictures
drwxr-xr-x   31 al  al     1054 Oct 15 17:09 tmp
drwxr-xr-x   19 al  al      646 Jul 20 19:29 Work
drwxr-xr-x+  23 al  al      782 Jun 20 11:43 Sites
drwxr-xr-x    9 al  al      306 May 20 19:52 AlexanderConsulting
drwxr-xr-x   18 al  al      612 Apr 20  2009 Reference
drwxr-xr-x    5 al  al      170 Apr  4  2009 GarageBandProjects
drwxr-xr-x    9 al  al      306 Mar 19  2009 tomcat6
drwxr-xr-x    4 al  al      136 Mar 12  2009 Workspaces
drwx------+   9 al  al      306 Jan  2  2009 Music
drwxr-xr-x   10 al  al      340 Mar  9  2008 XcodeProjects
drwx------+   8 al  al      272 Sep  9  2007 Movies
drwxr-xr-x   11 al  al      374 Aug 19  2007 AudioRecordings
drwxr-xr-x    4 al  al      136 Jul 19  2007 Apple Stuff
drwxr-xr-x    3 al  al      102 Feb 18  2007 DefaultEclipseWorkspace
drwxr-xr-x    3 al  al      102 Jan 14  2007 Apps
-rw-r--r--@   1 al  al     7608 Apr  1  2006 MYSQL_README
drwxr-xr-x+   5 al  al      170 Apr  1  2006 Public

In this ls command, the -t argument to the ls command gives us the sorting by file modification time, and the -l argument gives us this long/wide output.

To do the opposite, and sort the ls output by modification time from oldest to newest, just add the -r argument to the ls command, like this:

ls -ltr

Sort Unix ls command output by file size

What I just learned is that you can sort the ls command output by file size without piping the ls output into the Linux sort command. All you have to do is use the -S argument (that's an uppercase letter 'S') to your Unix or Linux ls command, like this:

ls -lS

(Note that those last two characters are a lowercase letter 'L' and and uppercase letter 'S'.)

Here's some sample output from that command:

total 49288
-rwx------   1 al  al  25232591 Sep 11  2008 apache-cxf-2.1.2.zip
drwxr-xr-x  13 al  al       442 Sep 11  2008 lib
drwxr-xr-x  10 al  al       340 Sep 11  2008 test-clients
drwxr-xr-x   9 al  al       306 Sep 11  2008 src
drwxr-xr-x   5 al  al       170 Sep 11  2008 build
drwxr-xr-x   4 al  al       136 Sep 11  2008 cobertura
drwxr-xr-x   3 al  al       102 Sep 11  2008 sql
drwxr-xr-x   3 al  al       102 Sep 11  2008 src-tests
drwxr-xr-x   2 al  al        68 Sep 11  2008 bin
drwxr-xr-x   2 al  al        68 Sep 11  2008 reports
drwxr-xr-x   2 al  al        68 Sep 11  2008 target
drwxr-xr-x   2 al  al        68 Sep 11  2008 temp

Alternatively, to sort by filesize from smallest to largest, again just add the -r option to reverse the default sort, as shown in this ls command example:

ls -lSr

Here's that command, followed by its output for the same directory shown in the previous command:

$ ls -lSr

total 49288
drwxr-xr-x   2 al  al        68 Sep 11  2008 temp
drwxr-xr-x   2 al  al        68 Sep 11  2008 target
drwxr-xr-x   2 al  al        68 Sep 11  2008 reports
drwxr-xr-x   2 al  al        68 Sep 11  2008 bin
drwxr-xr-x   3 al  al       102 Sep 11  2008 src-tests
drwxr-xr-x   3 al  al       102 Sep 11  2008 sql
drwxr-xr-x   4 al  al       136 Sep 11  2008 cobertura
drwxr-xr-x   5 al  al       170 Sep 11  2008 build
drwxr-xr-x   9 al  al       306 Sep 11  2008 src
drwxr-xr-x  10 al  al       340 Sep 11  2008 test-clients
drwxr-xr-x  13 al  al       442 Sep 11  2008 lib
-rwx------   1 al  al  25232591 Sep 11  2008 apache-cxf-2.1.2.zip

Unix ls command - sort by filename extension

Another cool thing I didn't know is that you can also sort ls command output by filename extension. All you have to do is use the "-X" argument, as shown in this example:

ls -1X

(The arguments there are the number one (1) and the capital letter 'X'. I use the number one to get single column output, so you can see the filename extensions more easily.)

In a different directory that's full of files with different filename extensions, this command results in the following sorted output:

mission-statement.shtml
navbar.shtml
new.shtml
sitemap.shtml
siteOfDay.shtml
sites.tgz
CHANGELOG.txt
COPYRIGHT.txt
INSTALL.mysql.txt
INSTALL.pgsql.txt
INSTALL.txt
LICENSE.txt
MAINTAINERS.txt
robots.txt
UPGRADE.txt
sitemap.xml

To show that there's nothing magical about the number one in that previous command, here's a similar command, where I combine the 'X' with the lowercase letter 'L' to get long ls output, sorted by filename extension. Here's this ls command, followed by its output, in that same directory:

$ ls -lX

-rwxr-xr-x  1 root root      7023 Apr  6  2000 mission-statement.shtml
-rw-r--r--  1 root root       573 Sep 25  2007 navbar.shtml
-rwxr-xr-x  1 root root      5430 Sep 16 22:57 sitemap.shtml
-rw-r--r--  1 root root        72 Mar 10  2001 siteOfDay.shtml
-rw-r--r--  1 root root   5900935 Sep 19 19:37 sites.tgz
-rw-r--r--  1 1080   1080   43058 Sep 16 15:34 CHANGELOG.txt
-rw-r--r--  1 1080   1080     988 Sep 14 08:50 COPYRIGHT.txt
-rw-r--r--  1 1080   1080    1308 Nov 19  2007 INSTALL.mysql.txt
-rw-r--r--  1 1080   1080    1075 Nov 26  2007 INSTALL.pgsql.txt
-rw-r--r--  1 1080   1080   15646 Jul  9  2008 INSTALL.txt
-rw-r--r--  1 1080   1080   18048 Jan  6  2009 LICENSE.txt
-rw-r--r--  1 1080   1080    1924 Apr 29 13:15 MAINTAINERS.txt
-rw-r--r--  1 1080   1080    1590 Dec 10  2008 robots.txt
-rw-r--r--  1 1080   1080    5002 Jan  4  2008 UPGRADE.txt
-rw-r--r--  1 root root      1840 May 17 11:21 sitemap.xml

How to reverse ls command output

Just to emphasize the point, you can reverse the output from any ls command with the "-r" argument.

Other Unix/Linux ls file sort options

There are more ways to sort the ls command output, but I think those are the most common methods. But to be a little more complete, here is a list of ls sorting options I just pulled from the CentOS Linux ls command man page:

-c    with -lt: sort by, and show, ctime (time of last modification of file 
      status information) 
      with -l: show ctime and sort by name otherwise: sort by ctime

-f    do not sort, enable -aU, disable -lst

-r, --reverse
      reverse order while sorting

-t    sort by modification time

-u    with  -lt:  sort by, and show, access time 
      with -l: show access time and sort by name 
      otherwise: sort by access time

-U    do not sort; list entries in directory order. 
      In combination with one_per_line format '-1',
      it will show files immediately and it has no 
      memory limitations.

-v    sort by version

--sort=WORD
      extension -X, none -U, size -S, time -t, version -v, status -c, time -t, atime -u, access -u, use -u

Mac OS X ls command difference

One quick note: I just tried some of these commands on Mac OS X 10.5.x, and the -X option does not work. All the other ls command sorting options worked as shown.

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