In Linux or Unix, ls is the command used to list the contents of a directory. When displaying the files and folders in the directory, it is sometimes more informative to have them sorted by name, size or an another attribute. The ls command does provide some sorting options that are commonly used, such as sorting by name, last modified time, last accessed time and file size.

It also provides an option (–reverse or -r) to reverse the sorting order and can be used in conjunction with any and all of the sorting options.

Sort by Name

By default, the ls command sorts by name: that is file name or the folder name.

bash$ ls -1

You can reverse the sort order by specifying the -r option

bash$ ls -1r

By default the files and folders are sorted together. If you prefer to sort the folders separately and be displayed before the files, then you can use the –group-directories-first option.

bash$ ls -lr --group-directories-first

Sort by Last Modified

In order to sort the contents by the last modified time, you should use the -t option

bash$ ls -t

This will sort the output by the last modified time with the newest being listed first. In order to sort the output list by the oldest file, you can use the –reverse (-r) option.

bash$ ls -tr

Sort by File Size

You can sort the contents by size of the file with the largest size being listed first, by using the -S option.

bash$ ls -S

You can sort the output to show the smallest file first by using the reverse (-r) option

bash$ ls -Sr

Sort by Extension

Another option (-X) provides the ability to sort by extension. This allows you to display files grouped by extensions.

bash$ ls -X

Again you can use the reverse option to sort in reverse order.

Though ls provides some sorting options as mentioned above, it does not have the ability to sort by many of the other file attributes, such as owner name or group name. But you can still sort by these fields by piping the output through to the sort command.

Using the sort command

In order to use the sort command to sort the output of ls, you should make sure that the field that you want to sort by is displayed by the ls command. The -l option prints out the long listing format which works for most cases.

bash$ ls -l

This will print out the attributes in a column mode. Now find the field or attribute that you want to sort by and its column or field number. Just count out the columns, for example in the above sample output the month is column 6 and the file name is column 9. Depending on the ls version and the options you use, the columns can change.

To sort by a particular column, pipe the output of the ls to the sort command and specify the column or field number. So, to sort by owner name, which is in field 3 you would do

bash$ ls -l | sort -k 3

To sort by owner and then by the filename which is field or column 9…

bash$ ls -l | sort -k 3,3 -k 9

Another useful command to know is the awk, which will actually let you prune the output to just the desired fields. This allows for an easier sorting and cleaner display.

For example, if you want to display only the owner, size and filename and then sort it by the owner name, then you could do something like

bash$ ls -lisa | awk '{print $5, $7, $11}' | sort

Note that the column and field numbers are a bit different in the above command output as I used other options with ls in addition to -l.