How can you list all file names beginning with S?

Linux commands can provide details on files and show options for customizing file listings, but can also reach as deeply into a file system as you care to look.

There are many ways to list files and display information about them on Linux systems. This post reviews a number of commands that provide details on files and provides options for customizing your file listings to meet your needs.

Most of the commands list files within individual directories while others reach as deeply into a file system as you care to look.

The primary command for listing files is, of course, ls. This command, however, has an extensive number of options for finding and listing just the files you want to see. Plus, there's always find for helping with very specific file searches.

Listing files by name

The easiest way to list files by name is simply to list them using the ls command. Listing files by name (alphanumeric order) is, after all, the default. You can choose the ls (no details) or ls -l (lots of details) to determine your view.

Pipe the output of ls to the more command if you want to review your listing a screenful at a time.

Listing files in reverse name order

To reverse the listing of files by name, add the -r (reverse) option. This will be like turning the normal listing upside down.

Listing files by file extension

The ls command doesn’t analyze file types by content, but works with file names. There is, however, a command option that can list files by extension. If you add the -X option, ls will sort files by name within each extension category. For example, it will list files without extensions first (in alphanumeric order) followed by files with extensions like .1, .bz2, .c and so on.

Listing directories only

By default, the ls command will show both files and directories. If you want to list only directories, you can use the -d option. You will get a listing like this one:

Listing files by size

If you want to list files in size order, add the -S option. Note, however, that this won't actually show you the sizes (along with other file details) unless you also add the -l (long listing) option. When listing files by size, it's generally helpful to see that the command is doing what you asked. Notice that the default is to show the largest files first. Add the -r option to reverse this (i.e., ls -lSr).

Listing files by owner

If you want to list files by owner (e.g., in a shared directory), you can pass the output of the ls command to sort and pick out the owner column by adding -k3 to sort on the third field.

In fact, you can sort on any field this way (e.g., year). Just be careful to add an “n” – -k5n – if you’re sorting on a field which is numeric or you'll be sorting in alphanumeric order. This sorting technique is useful for sorting file contents as well, not just listing files.

Listing files by age

Use the -t option to list files in order of age – how new they are. Add the -r option to get the most recently updated files showing up last in the list. I use this alias to show me a list of the files that I’ve most recently updated:

Note that file change and modification times are different. The -c (change) and -t (modification) options will not always give the same results. If you change permissions on a file and nothing else, -c will put that files at the top of the ls output while -t will not. If you’re curious about the difference, look at the output of the stat command.

Listing files by group

To sort files by the associated groups, you can pass the output from a long listing to the sort command and tell it to sort on column 4.

Listing files by access date

To list files by access date (most recently accessed first), use the -ltu options. The "u" enforces the "by access date" listing order.

Listing multiple files on a single line

Sometimes a condensed file listing is more appropriate for the task at hand. The ls command even has options for that. To list files on as few lines as possible, you can use --format=comma to separate file names with commas as in this command:

Prefer white space? Use --format=across instead.

Adding depth to your searches

While ls generally lists files in a single directory, you can choose instead to recursively list files by using the -R options, delving into the entire depth of directories:

Alternately, you can use a find command with a limited or unlimited depth specification. In this command, we instruct the find command to look in only three levels of directories:

Choosing ls vs find

When you need to list files that meet a very selective list of requirements, the find command is probably a better tool to use than ls.

Unlike ls, the find command looks as deeply as possible unless you constrain it. It also has many other options and an -exec command that allows you to take some specific action once you find the files you’re looking for.

Wrap-Up

The ls command has a lot of options for listing files. Check them out. You might find some that you’ll love.

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Sandra Henry-Stocker has been administering Unix systems for more than 30 years. She describes herself as "USL" (Unix as a second language) but remembers enough English to write books and buy groceries. She lives in the mountains in Virginia where, when not working with or writing about Unix, she's chasing the bears away from her bird feeders.

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